Hello.
My laptop is a Dell Inspiron 1525.

uname -a gives :
Linux Ubuntu 2.6.35-29-generic #51-Ubuntu SMP Fri Apr 15 17:12:35 UTC 2011 x86_64 GNU/Linux

When updating graphically from 11.04 (64bits) to 11.11, i got the alert message :

Invalid package information
After your package information was updated the essential package 'ubuntu-minimal' can not be found anymore.
This indicates a serious error, please report this bug against the 'update-manager' package and include the files in /var/log/dist-upgrade/ in the bug report.

so here it is :

Content of file /var/log/dist-upgrade/main.log :

2011-04-29 14:05:49,622 INFO Using config files '['./DistUpgrade.cfg']'
2011-04-29 14:05:49,622 INFO uname information: 'Linux Ubuntu 2.6.35-29-generic #51-Ubuntu SMP Fri Apr 15 17:12:35 UTC 2011 x86_64'
2011-04-29 14:05:49,622 INFO release-upgrader version '0.150' started
2011-04-29 14:05:49,829 DEBUG svg pixbuf loader failed (Error displaying image)
2011-04-29 14:05:50,616 DEBUG Using 'DistUpgradeViewGtk' view
2011-04-29 14:05:50,658 DEBUG aufsOptionsAndEnvironmentSetup()
2011-04-29 14:05:50,659 DEBUG using '/tmp/upgrade-rw-8QMen3' as aufs_rw_dir
2011-04-29 14:05:50,660 DEBUG using '/tmp/upgrade-chroot-9r4W3B' as aufs chroot dir
2011-04-29 14:05:50,660 DEBUG enable dpkg --force-overwrite
2011-04-29 14:05:50,681 DEBUG creating statefile: '/var/log/dist-upgrade/apt-clone_system_state.tar.gz'
2011-04-29 14:05:53,597 DEBUG lsb-release: 'maverick'
2011-04-29 14:05:53,598 DEBUG _pythonSymlinkCheck run
2011-04-29 14:05:53,602 DEBUG openCache()
2011-04-29 14:05:53,987 DEBUG /openCache(), new cache size 32283
2011-04-29 14:05:53,987 DEBUG needServerMode(): run in 'desktop' mode, (because of pkg 'ubuntu-desktop')
2011-04-29 14:05:53,988 DEBUG checkViewDepends()
2011-04-29 14:05:53,988 DEBUG running doUpdate() (showErrors=False)
2011-04-29 14:05:58,681 ERROR IOError/SystemError in cache.update(): 'W:Failed to fetch http://fr.archive.ubuntu.com/ubuntu/dists/maverick-updates/universe/source/Sources.gz  Hash Sum mismatch
, W:Failed to fetch http://fr.archive.ubuntu.com/ubuntu/dists/maverick-updates/main/binary-amd64/Packages.gz  Hash Sum mismatch
, E:Some index files failed to download, they have been ignored, or old ones used instead.'. Retrying (currentRetry: 0)
2011-04-29 14:05:58,681 ERROR doUpdate() failed completely
2011-04-29 14:05:58,681 DEBUG openCache()
2011-04-29 14:05:59,087 DEBUG /openCache(), new cache size 32283
2011-04-29 14:05:59,087 DEBUG doPostInitialUpdate
2011-04-29 14:05:59,088 DEBUG Plugin modules in ./plugins: dpkg_status_plugin.py kdelibs4to5_plugin.py langpack_manual_plugin.py deb_plugin.py remove_lilo_plugin.py
2011-04-29 14:05:59,088 DEBUG Loading module ./plugins/dpkg_status_plugin.py
2011-04-29 14:05:59,092 DEBUG Plugins in <module 'dpkg_status_plugin' from './plugins/dpkg_status_plugin.py'>: <class 'dpkg_status_plugin.DpkgStatusPlugin'>
2011-04-29 14:05:59,092 DEBUG Loading module ./plugins/kdelibs4to5_plugin.py
2011-04-29 14:05:59,093 DEBUG Plugins in <module 'kdelibs4to5_plugin' from './plugins/kdelibs4to5_plugin.py'>: <class 'kdelibs4to5_plugin.Kdelibs4devToKdelibs5devPlugin'>
2011-04-29 14:05:59,093 DEBUG Loading module ./plugins/langpack_manual_plugin.py
2011-04-29 14:05:59,095 DEBUG Plugins in <module 'langpack_manual_plugin' from './plugins/langpack_manual_plugin.py'>: <class 'langpack_manual_plugin.MarkLangpacksManuallyInstalledPlugin'>
2011-04-29 14:05:59,095 DEBUG Loading module ./plugins/deb_plugin.py
2011-04-29 14:05:59,096 DEBUG Plugins in <module 'deb_plugin' from './plugins/deb_plugin.py'>: <class 'deb_plugin.DebPlugin'>
2011-04-29 14:05:59,096 DEBUG Loading module ./plugins/remove_lilo_plugin.py
2011-04-29 14:05:59,097 DEBUG Plugins in <module 'remove_lilo_plugin' from './plugins/remove_lilo_plugin.py'>: <class 'remove_lilo_plugin.RemoveLiloPlugin'>
2011-04-29 14:05:59,097 DEBUG plugins for condition 'PostInitialUpdate' are '[]'
2011-04-29 14:05:59,097 DEBUG plugins for condition 'nattyPostInitialUpdate' are '[]'
2011-04-29 14:05:59,097 DEBUG plugins for condition 'from_maverickPostInitialUpdate' are '[]'
2011-04-29 14:06:07,582 DEBUG Foreign: python-wxgtk2.8 python-wxversion firefox firefox-branding sun-java6-bin language-pack-en ubufox firefox-globalmenu virtualbox-4.0 opera libwxgtk2.8-0 language-pack-en-base sun-java6-jre xul-ext-ubufox python-wxtools libwxbase2.8-0 firefox-gnome-support
2011-04-29 14:06:07,582 DEBUG Obsolete: 
2011-04-29 14:06:07,584 DEBUG updateSourcesList()
2011-04-29 14:06:07,674 DEBUG rewriteSourcesList()
2011-04-29 14:06:07,683 DEBUG examining: 'deb http://fr.archive.ubuntu.com/ubuntu/ maverick main restricted'
2011-04-29 14:06:07,683 DEBUG entry 'deb http://fr.archive.ubuntu.com/ubuntu/ natty main restricted' updated to new dist
2011-04-29 14:06:07,684 DEBUG examining: 'deb-src http://fr.archive.ubuntu.com/ubuntu/ maverick main restricted'
2011-04-29 14:06:07,684 DEBUG entry 'deb-src http://fr.archive.ubuntu.com/ubuntu/ natty main restricted' updated to new dist
2011-04-29 14:06:07,684 DEBUG examining: 'deb http://fr.archive.ubuntu.com/ubuntu/ maverick-updates main restricted'
2011-04-29 14:06:07,684 DEBUG entry 'deb http://fr.archive.ubuntu.com/ubuntu/ natty-updates main restricted' updated to new dist
2011-04-29 14:06:07,684 DEBUG examining: 'deb-src http://fr.archive.ubuntu.com/ubuntu/ maverick-updates main restricted'
2011-04-29 14:06:07,684 DEBUG entry 'deb-src http://fr.archive.ubuntu.com/ubuntu/ natty-updates main restricted' updated to new dist
2011-04-29 14:06:07,684 DEBUG examining: 'deb http://fr.archive.ubuntu.com/ubuntu/ maverick universe'
2011-04-29 14:06:07,685 DEBUG entry 'deb http://fr.archive.ubuntu.com/ubuntu/ natty universe' updated to new dist
2011-04-29 14:06:07,685 DEBUG examining: 'deb-src http://fr.archive.ubuntu.com/ubuntu/ maverick universe'
2011-04-29 14:06:07,685 DEBUG entry 'deb-src http://fr.archive.ubuntu.com/ubuntu/ natty universe' updated to new dist
2011-04-29 14:06:07,685 DEBUG examining: 'deb http://fr.archive.ubuntu.com/ubuntu/ maverick-updates universe'
2011-04-29 14:06:07,685 DEBUG entry 'deb http://fr.archive.ubuntu.com/ubuntu/ natty-updates universe' updated to new dist
2011-04-29 14:06:07,685 DEBUG examining: 'deb-src http://fr.archive.ubuntu.com/ubuntu/ maverick-updates universe'
2011-04-29 14:06:07,685 DEBUG entry 'deb-src http://fr.archive.ubuntu.com/ubuntu/ natty-updates universe' updated to new dist
2011-04-29 14:06:07,686 DEBUG examining: 'deb http://fr.archive.ubuntu.com/ubuntu/ maverick multiverse'
2011-04-29 14:06:07,686 DEBUG entry 'deb http://fr.archive.ubuntu.com/ubuntu/ natty multiverse' updated to new dist
2011-04-29 14:06:07,686 DEBUG examining: 'deb-src http://fr.archive.ubuntu.com/ubuntu/ maverick multiverse'
2011-04-29 14:06:07,686 DEBUG entry 'deb-src http://fr.archive.ubuntu.com/ubuntu/ natty multiverse' updated to new dist
2011-04-29 14:06:07,686 DEBUG examining: 'deb http://fr.archive.ubuntu.com/ubuntu/ maverick-updates multiverse'
2011-04-29 14:06:07,686 DEBUG entry 'deb http://fr.archive.ubuntu.com/ubuntu/ natty-updates multiverse' updated to new dist
2011-04-29 14:06:07,686 DEBUG examining: 'deb-src http://fr.archive.ubuntu.com/ubuntu/ maverick-updates multiverse'
2011-04-29 14:06:07,687 DEBUG entry 'deb-src http://fr.archive.ubuntu.com/ubuntu/ natty-updates multiverse' updated to new dist
2011-04-29 14:06:07,687 DEBUG examining: 'deb http://fr.archive.ubuntu.com/ubuntu/ maverick-backports main restricted universe multiverse'
2011-04-29 14:06:07,687 DEBUG entry 'deb http://fr.archive.ubuntu.com/ubuntu/ natty-backports main restricted universe multiverse' updated to new dist
2011-04-29 14:06:07,687 DEBUG examining: 'deb http://archive.canonical.com/ubuntu maverick partner'
2011-04-29 14:06:07,687 DEBUG entry 'deb http://archive.canonical.com/ubuntu natty partner' updated to new dist
2011-04-29 14:06:07,687 DEBUG examining: 'deb-src http://archive.canonical.com/ubuntu maverick partner'
2011-04-29 14:06:07,688 DEBUG entry 'deb-src http://archive.canonical.com/ubuntu natty partner' updated to new dist
2011-04-29 14:06:07,688 DEBUG examining: 'deb http://extras.ubuntu.com/ubuntu maverick main'
2011-04-29 14:06:07,688 DEBUG entry 'deb http://extras.ubuntu.com/ubuntu natty main' updated to new dist
2011-04-29 14:06:07,688 DEBUG examining: 'deb-src http://extras.ubuntu.com/ubuntu maverick main'
2011-04-29 14:06:07,688 DEBUG entry 'deb-src http://extras.ubuntu.com/ubuntu natty main' updated to new dist
2011-04-29 14:06:07,688 DEBUG examining: 'deb http://security.ubuntu.com/ubuntu maverick-security main restricted'
2011-04-29 14:06:07,688 DEBUG entry 'deb http://security.ubuntu.com/ubuntu natty-security main restricted' updated to new dist
2011-04-29 14:06:07,689 DEBUG examining: 'deb-src http://security.ubuntu.com/ubuntu maverick-security main restricted'
2011-04-29 14:06:07,689 DEBUG entry 'deb-src http://security.ubuntu.com/ubuntu natty-security main restricted' updated to new dist
2011-04-29 14:06:07,689 DEBUG examining: 'deb http://security.ubuntu.com/ubuntu maverick-security universe'
2011-04-29 14:06:07,689 DEBUG entry 'deb http://security.ubuntu.com/ubuntu natty-security universe' updated to new dist
2011-04-29 14:06:07,689 DEBUG examining: 'deb-src http://security.ubuntu.com/ubuntu maverick-security universe'
2011-04-29 14:06:07,689 DEBUG entry 'deb-src http://security.ubuntu.com/ubuntu natty-security universe' updated to new dist
2011-04-29 14:06:07,689 DEBUG examining: 'deb http://security.ubuntu.com/ubuntu maverick-security multiverse'
2011-04-29 14:06:07,690 DEBUG entry 'deb http://security.ubuntu.com/ubuntu natty-security multiverse' updated to new dist
2011-04-29 14:06:07,690 DEBUG examining: 'deb http://fr.archive.ubuntu.com/ubuntu/ maverick-proposed restricted main multiverse universe'
2011-04-29 14:06:07,690 DEBUG entry 'deb http://fr.archive.ubuntu.com/ubuntu/ natty-proposed restricted main multiverse universe' updated to new dist
2011-04-29 14:06:07,690 DEBUG examining: 'deb-src http://security.ubuntu.com/ubuntu maverick-security multiverse'
2011-04-29 14:06:07,690 DEBUG entry 'deb-src http://security.ubuntu.com/ubuntu natty-security multiverse' updated to new dist
2011-04-29 14:06:07,690 DEBUG examining: 'deb http://deb.opera.com/opera/ stable non-free'
2011-04-29 14:06:07,694 DEBUG entry '# deb http://deb.opera.com/opera/ stable non-free # disabled on upgrade to natty' was disabled (unknown mirror)
2011-04-29 14:06:07,694 DEBUG examining: 'deb http://deb.torproject.org/torproject.org maverick main'
2011-04-29 14:06:07,698 DEBUG entry '# deb http://deb.torproject.org/torproject.org natty main # disabled on upgrade to natty' was disabled (unknown mirror)
2011-04-29 14:06:07,699 DEBUG examining: 'deb http://download.virtualbox.org/virtualbox/debian maverick contrib non-free'
2011-04-29 14:06:07,702 DEBUG entry '# deb http://download.virtualbox.org/virtualbox/debian natty contrib non-free # disabled on upgrade to natty' was disabled (unknown mirror)
2011-04-29 14:06:07,703 DEBUG examining: 'deb http://apt.wxwidgets.org/ lucid-wx main'
2011-04-29 14:06:07,706 DEBUG entry '# deb http://apt.wxwidgets.org/ lucid-wx main # disabled on upgrade to natty' was disabled (unknown mirror)
2011-04-29 14:06:07,707 DEBUG examining: 'deb-src http://apt.wxwidgets.org/ lucid-wx main'
2011-04-29 14:06:07,710 DEBUG entry '# deb-src http://apt.wxwidgets.org/ lucid-wx main # disabled on upgrade to natty' was disabled (unknown mirror)
2011-04-29 14:06:07,711 DEBUG examining: 'deb http://archive.ubuntu.com/ubuntu maverick-backports main universe multiverse restricted'
2011-04-29 14:06:07,711 DEBUG entry 'deb http://archive.ubuntu.com/ubuntu natty-backports main universe multiverse restricted' updated to new dist
2011-04-29 14:06:07,711 DEBUG examining: 'deb-src http://archive.ubuntu.com/ubuntu maverick-backports main universe multiverse restricted'
2011-04-29 14:06:07,711 DEBUG entry 'deb-src http://archive.ubuntu.com/ubuntu natty-backports main universe multiverse restricted' updated to new dist
2011-04-29 14:06:07,711 DEBUG examining: 'deb http://ppa.launchpad.net/mozillateam/firefox-stable/ubuntu maverick main'
2011-04-29 14:06:07,715 DEBUG entry '# deb http://ppa.launchpad.net/mozillateam/firefox-stable/ubuntu natty main # disabled on upgrade to natty' was disabled (unknown mirror)
2011-04-29 14:06:10,065 DEBUG running doUpdate() (showErrors=True)
2011-04-29 14:06:30,177 DEBUG openCache()
2011-04-29 14:06:30,178 DEBUG failed to SystemUnLock() (E:Not locked) 
2011-04-29 14:06:30,561 DEBUG /openCache(), new cache size 2817
2011-04-29 14:06:30,562 DEBUG needServerMode(): run in 'desktop' mode, (because of pkg 'ubuntu-desktop')
2011-04-29 14:06:30,562 ERROR No 'ubuntu-minimal' available/downloadable after sources.list rewrite+update


Content of /var/log/dist-upgrade/lspci.txt :

00:00.0 Host bridge [0600]: Intel Corporation Mobile PM965/GM965/GL960 Memory Controller Hub [8086:2a00] (rev 0c)
00:02.0 VGA compatible controller [0300]: Intel Corporation Mobile GM965/GL960 Integrated Graphics Controller [8086:2a02] (rev 0c)
00:02.1 Display controller [0380]: Intel Corporation Mobile GM965/GL960 Integrated Graphics Controller [8086:2a03] (rev 0c)
00:1a.0 USB Controller [0c03]: Intel Corporation 82801H (ICH8 Family) USB UHCI Controller #4 [8086:2834] (rev 02)
00:1a.1 USB Controller [0c03]: Intel Corporation 82801H (ICH8 Family) USB UHCI Controller #5 [8086:2835] (rev 02)
00:1a.7 USB Controller [0c03]: Intel Corporation 82801H (ICH8 Family) USB2 EHCI Controller #2 [8086:283a] (rev 02)
00:1b.0 Audio device [0403]: Intel Corporation 82801H (ICH8 Family) HD Audio Controller [8086:284b] (rev 02)
00:1c.0 PCI bridge [0604]: Intel Corporation 82801H (ICH8 Family) PCI Express Port 1 [8086:283f] (rev 02)
00:1c.1 PCI bridge [0604]: Intel Corporation 82801H (ICH8 Family) PCI Express Port 2 [8086:2841] (rev 02)
00:1c.4 PCI bridge [0604]: Intel Corporation 82801H (ICH8 Family) PCI Express Port 5 [8086:2847] (rev 02)
00:1d.0 USB Controller [0c03]: Intel Corporation 82801H (ICH8 Family) USB UHCI Controller #1 [8086:2830] (rev 02)
00:1d.1 USB Controller [0c03]: Intel Corporation 82801H (ICH8 Family) USB UHCI Controller #2 [8086:2831] (rev 02)
00:1d.2 USB Controller [0c03]: Intel Corporation 82801H (ICH8 Family) USB UHCI Controller #3 [8086:2832] (rev 02)
00:1d.7 USB Controller [0c03]: Intel Corporation 82801H (ICH8 Family) USB2 EHCI Controller #1 [8086:2836] (rev 02)
00:1e.0 PCI bridge [0604]: Intel Corporation 82801 Mobile PCI Bridge [8086:2448] (rev f2)
00:1f.0 ISA bridge [0601]: Intel Corporation 82801HEM (ICH8M) LPC Interface Controller [8086:2815] (rev 02)
00:1f.1 IDE interface [0101]: Intel Corporation 82801HBM/HEM (ICH8M/ICH8M-E) IDE Controller [8086:2850] (rev 02)
00:1f.2 SATA controller [0106]: Intel Corporation 82801HBM/HEM (ICH8M/ICH8M-E) SATA AHCI Controller [8086:2829] (rev 02)
00:1f.3 SMBus [0c05]: Intel Corporation 82801H (ICH8 Family) SMBus Controller [8086:283e] (rev 02)
02:09.0 FireWire (IEEE 1394) [0c00]: Ricoh Co Ltd R5C832 IEEE 1394 Controller [1180:0832] (rev 05)
02:09.1 SD Host controller [0805]: Ricoh Co Ltd R5C822 SD/SDIO/MMC/MS/MSPro Host Adapter [1180:0822] (rev 22)
02:09.2 System peripheral [0880]: Ricoh Co Ltd R5C592 Memory Stick Bus Host Adapter [1180:0592] (rev 12)
02:09.3 System peripheral [0880]: Ricoh Co Ltd xD-Picture Card Controller [1180:0852] (rev 12)
09:00.0 Ethernet controller [0200]: Marvell Technology Group Ltd. 88E8040 PCI-E Fast Ethernet Controller [11ab:4354] (rev 12)
0b:00.0 Network controller [0280]: Broadcom Corporation BCM4312 802.11b/g LP-PHY [14e4:4315] (rev 01)