Here is how to implement the “nomodeset” option in Karmic:

1. Open the Terminal and do:

sudo gedit /etc/default/grub

2. The file opens in gedit. Find the line that says:

GRUB_CMDLINE_LINUX=”"

and change it to:

GRUB_CMDLINE_LINUX=”nomodeset“

3. Save the file and close gedit.

4. In the Terminal run:

sudo update-grub

DONE! Reboot …