I've noticed that after running X, if I go back to a console window (either by pressing ctrl-alt-f1 or by killing X) then my console font is corrupted. The console font is normally set to 8x8 (for an 80x50 screen) with "vga=0x0f01" given to the kernel as a boot parameter.
You can see the corruption in this picture: http://www.cobbleware.com/files/consolefont.jpg
It seems that the screen has gone back to an 80x28 (or whatever) layout, with the bottom half of each line repeated. Linux still thinks that the console is 80x50, so the command prompt is somewhere off the bottom of the screen.
This is on kernel 2.6.19-rc4-mm2 or something, but it also happens on 2.6.18. The card is a 7800GT.
I'll attach a bug report too, just in case it's useful. Note that this is not a major issue for me, but I thought you might like to know about it