problem upgrading from 10.10 to 11.04

[Noel-emma]

when upgrading the version using update manager, firstly this mesage appears on the first step of the upgrade (preparing to upgrade):

Third sources disabled
 Some third party entries in your sources.list were disabled. You can re-enable them after the upgrade with the 'software-properties' tool or your package manager.

then on step 2 of the update (setting new software channels) this message appears:

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.

after which it restors the previous version and the upgrade stops.

all updates have been done before the upgrade.

ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: linux-image-2.6.35-29-generic 2.6.35-29.51
Regression: No
Reproducible: Yes
ProcVersionSignature: Ubuntu 2.6.35-29.51-generic 2.6.35.12
Uname: Linux 2.6.35-29-generic x86_64
NonfreeKernelModules: nvidia
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.23.
AplayDevices:
 **** List of PLAYBACK Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: STAC92xx Analog [STAC92xx Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: noel 1529 F.... pulseaudio
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xdffdc000 irq 44'
   Mixer name : 'SigmaTel STAC9227'
   Components : 'HDA:83847618,102801dd,00100201'
   Controls : 30
   Simple ctrls : 21
Date: Fri Apr 29 11:10:14 2011
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release amd64 (20101007)
MachineType: Dell Inc. Dell DM061
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.35-29-generic root=/dev/sda1 loop=/hostname/disks/root.disk ro splash vga=789 quiet splash
ProcEnviron:
 LANG=en_GB.utf8
 SHELL=/bin/bash
RelatedPackageVersions: linux-firmware 1.38.7
RfKill:
 0: phy0: Wireless LAN
  Soft blocked: no
  Hard blocked: no
SourcePackage: linux
dmi.bios.date: 03/30/2007
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 2.3.2
dmi.board.name: 0WG864
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 6
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvr2.3.2:bd03/30/2007:svnDellInc.:pnDellDM061:pvr:rvnDellInc.:rn0WG864:rvr:cvnDellInc.:ct6:cvr:
dmi.product.name: Dell DM061
dmi.sys.vendor: Dell Inc.

[Oto Buchta (tapik)]

I run Ubuntu 10.10 on HP 6235s
$ uname -a
Linux hurin 2.6.35-28-generic #50-Ubuntu SMP Fri Mar 18 19:00:26 UTC 2011 i686 GNU/Linux