This will seems quite bizarre but that's a huge problem for me, I'm facing it for a long time since Ubuntu 12.04.
My Ubuntu/Linux Mint/Debian (Unity/Gnome) always starts flickering after using the computer for a while, I always thought this had something to do with the video board.
I have an Vostro 3550 (Radeon 6xxx/Intel Onboard).
First I realized that when I was navigating trough an website, when i selected with the mouse a combo, the combo closed it self automatically then the screen starts flickering.
The i realized when i was trying to make the login in the terminal (crtl + alt + f1) a strange character appears, like: ^@ repeatedly.
When i keep CRTL pressed the system never flickers!
I have absolutely no problem using Windows.
What can i do? There is no such thing as Keyboard driver on Dell Support.
I would love to use Ubuntu only, but this is very annoying.
Problem happens on Ubuntu 12.04, .10 and 13.04 Linux Mint 15 (Cinnamon) Debian Live with Gnome