I am new to linux (apologies if i'm posting to the wrong forum)

I am currently running gentoo on a newly put together computer:

ASUS motherboard (P5LD2-VM)
Intel P4 3GHz chip
ASUS nVidia Geforce 6200TC video card (memory type DDR)
pqi POWER series 1GB (DDR2)
250 GB hard drive
etc...

I'm having a display problem that occurs after about 20 minutes into running the window manager (fluxbox). A pixellated striped pattern will show up when moving a window across the screen (looks like tv static). Sometime the color tint will change and repeat the screeenshot on the background. Highlighting or moving the mouse over the window and its contents will bring the text back into view. The display goes haywire faster when using xfce. I can get back to a normal display for a short bit of time by restarting the wm, but after a while the only thing that'll fix it is rebooting.

I just recently replaced the BIOS chip which i believe was corrupt (causing other problems and couldn't be flashed) but that does not seem to fix the display problems as i'd hoped.

I believe i have the correct horizontal and vertical sync rates correct for my monitor...

Question: Do you think this is a hardware issue or an installation error (newbie)?

Motherboard problem or a video card/memory compatibility issue?

Are DDR2 memory sticks compatible with a DDR-type video card?

Thanks!