Comment 9 for bug 251344

after restart in grub load press esc and select 2.6.24-19-generic for startup your ubuntu

after startup and nice look of ubuntu start sinaptic and search for 2.6.24-20 ,and remove next:

Completely removed the following packages:
linux-headers-2.6.24-20
linux-image-2.6.24-20-generic

Removed the following packages:
linux-headers-2.6.24-20-generic
linux-ubuntu-modules-2.6.24-20-generic
linux-headers-generic
linux-image-generic

restart computer
(if somebody dont anderstand sorry about my bad english :) )