I'm having the same problem since I upgraded some packages on 2-feb. I see that bcmwl-kernel-source, isc-dhcp-client and isc-dhcp-common where upgraded and then the problem started. Is there anyway of falling back to the previous version to check it?

I add the list of upgrades:
cat  /var/log/dpkg.log  | grep upgrade
2013-02-02 00:06:11 upgrade libdrm2 2.4.32-1ubuntu1 2.4.39-0ubuntu0.1
2013-02-02 00:06:12 upgrade libdrm-intel1 2.4.32-1ubuntu1 2.4.39-0ubuntu0.1
2013-02-02 00:06:13 upgrade libdrm-nouveau1a 2.4.32-1ubuntu1 2.4.39-0ubuntu0.1
2013-02-02 00:06:14 upgrade libdrm-radeon1 2.4.32-1ubuntu1 2.4.39-0ubuntu0.1
2013-02-02 00:06:15 upgrade google-chrome-stable 24.0.1312.56-r177594 24.0.1312.57-r178923
2013-02-02 00:06:22 upgrade libav-tools 4:0.8.4-0ubuntu0.12.04.1 4:0.8.5-0ubuntu0.12.04.1
2013-02-02 00:06:23 upgrade libpostproc52 4:0.8.4-0ubuntu0.12.04.1 4:0.8.5-0ubuntu0.12.04.1
2013-02-02 00:06:24 upgrade libavfilter2 4:0.8.4-0ubuntu0.12.04.1 4:0.8.5-0ubuntu0.12.04.1
2013-02-02 00:06:25 upgrade libswscale2 4:0.8.4-0ubuntu0.12.04.1 4:0.8.5-0ubuntu0.12.04.1
2013-02-02 00:06:26 upgrade libavdevice53 4:0.8.4-0ubuntu0.12.04.1 4:0.8.5-0ubuntu0.12.04.1
2013-02-02 00:06:27 upgrade libavformat53 4:0.8.4-0ubuntu0.12.04.1 4:0.8.5-0ubuntu0.12.04.1
2013-02-02 00:06:28 upgrade libavcodec-extra-53 4:0.8.4ubuntu0.12.04.1 4:0.8.5ubuntu0.12.04.1
2013-02-02 00:06:29 upgrade libavutil-extra-51 4:0.8.4ubuntu0.12.04.1 4:0.8.5ubuntu0.12.04.1
2013-02-02 00:06:30 upgrade libssh-4 0.5.2-1ubuntu0.12.04.1 0.5.2-1ubuntu0.12.04.2
2013-02-02 00:06:31 upgrade initramfs-tools 0.99ubuntu13 0.99ubuntu13.1
2013-02-02 00:06:32 upgrade initramfs-tools-bin 0.99ubuntu13 0.99ubuntu13.1
2013-02-02 00:06:45 upgrade isc-dhcp-client 4.1.ESV-R4-0ubuntu5.5 4.1.ESV-R4-0ubuntu5.6
2013-02-02 00:06:46 upgrade isc-dhcp-common 4.1.ESV-R4-0ubuntu5.5 4.1.ESV-R4-0ubuntu5.6
2013-02-02 00:06:47 upgrade upstart 1.5-0ubuntu7 1.5-0ubuntu7.2
2013-02-02 00:06:48 upgrade ubuntu-minimal 1.267 1.267.1
2013-02-02 00:06:49 upgrade plymouth-label 0.8.2-2ubuntu30 0.8.2-2ubuntu31
2013-02-02 00:06:50 upgrade plymouth 0.8.2-2ubuntu30 0.8.2-2ubuntu31
2013-02-02 00:06:51 upgrade libplymouth2 0.8.2-2ubuntu30 0.8.2-2ubuntu31
2013-02-02 00:06:52 upgrade plymouth-theme-ubuntu-text 0.8.2-2ubuntu30 0.8.2-2ubuntu31
2013-02-02 00:06:53 upgrade ubuntu-standard 1.267 1.267.1
2013-02-02 00:06:54 upgrade linux-libc-dev 3.2.0-36.57 3.2.0-37.58
2013-02-02 00:06:56 upgrade bcmwl-kernel-source 5.100.82.38+bdcom-0ubuntu6.1 6.20.155.1+bdcom-0ubuntu0.0.1
2013-02-02 00:10:50 upgrade checkbox 0.13.7 0.13.9
2013-02-02 00:10:53 upgrade checkbox-qt 0.13.7 0.13.9
2013-02-02 00:10:55 upgrade libtelepathy-glib0 0.18.0-1ubuntu1 0.18.2-0ubuntu1
2013-02-02 00:10:56 upgrade gir1.2-telepathyglib-0.12 0.18.0-1ubuntu1 0.18.2-0ubuntu1
2013-02-02 00:10:57 upgrade inkscape 0.48.3.1-1ubuntu1 0.48.3.1-1ubuntu1.1
2013-02-02 00:11:03 upgrade jockey-gtk 0.9.7-0ubuntu7.4 0.9.7-0ubuntu7.7
2013-02-02 00:11:04 upgrade jockey-common 0.9.7-0ubuntu7.4 0.9.7-0ubuntu7.7
2013-02-02 00:11:06 upgrade linux-generic-pae 3.2.0.36.43 3.2.0.37.44
2013-02-02 00:11:07 upgrade linux-image-generic-pae 3.2.0.36.43 3.2.0.37.44
2013-02-02 00:11:25 upgrade linux-headers-generic-pae 3.2.0.36.43 3.2.0.37.44
2013-02-02 00:11:26 upgrade plymouth-theme-ubuntu-logo 0.8.2-2ubuntu30 0.8.2-2ubuntu31
2013-02-02 00:11:27 upgrade ubuntu-desktop 1.267 1.267.1
2013-02-02 00:11:28 upgrade ffmpeg 4:0.8.4-0ubuntu0.12.04.1 4:0.8.5-0ubuntu0.12.04.1
2013-02-02 00:11:29 upgrade gnome-settings-daemon 3.4.2-0ubuntu0.6 3.4.2-0ubuntu0.6.1
2013-02-04 12:32:57 upgrade base-files 6.5ubuntu6.4 6.5ubuntu6.5
2013-02-04 12:33:48 upgrade linux-generic-pae 3.2.0.37.44 3.2.0.37.45
2013-02-04 12:33:49 upgrade linux-image-generic-pae 3.2.0.37.44 3.2.0.37.45
2013-02-04 12:33:50 upgrade linux-headers-generic-pae 3.2.0.37.44 3.2.0.37.45


Thanks!