I have installed Ubuntu 12.04 LTS on an IBM Thinkpad T41.
Up until Linux
3.2.0-30 generic everything was working fine. I accept all the software update.
3.2.0-31 generic the machine freezes and I get the error:
error couldn't read file Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
error: Cannot read the Linux header
then the machine returns to the Grub menu
3.2.0-30 still works fine if I select that.