Mac Pro Quad Core 2.8 - black screen when on Finder, but can see the starting process

Hi every one,
I had this problem for a while now. When I'm starting up my computer, the grey screen with apple logo display, and after a while, the screen become black with a strange noisy red square up right in my screen, I can hear my hard drive continue working but the screen is'n't displaying any finder image. I'have tried many things (starting with Command-Alt-P-R, Safe mode, Install disc, Command-R) but nothing seams to help. I have one remaining solution, it's to replace my GPU (nVidia GeForce 8800 GT 512 MB) but before spending money on it, I'm asking if someone have a clue if there is something I could try before.
Thanks for your help !

Here are three ideas:

1. Try booting the computer from a different hard drive (a 2nd hard drive with the Mac OS installed on it).
2. Try booting the computer from a Mac OS install disk.
3. Try removing & reinstalling the video card.
4. Try installing the video card in a different slot.

If none of these ideas help...then I would say the video card is at fault...and you need another video card.

- Nick

thanks for your tips, none of the 4 options fix the problem ( when I tried to change de video card to the other 16x PCI-slot, the noisy pattern changed from before but I could'nt see anything so... ), a new GPU coming up!!!

pac749 said:

thanks for your tips, none of the 4 options fix the problem ( when I tried to change de video card to the other 16x PCI-slot, the noisy pattern changed from before but I could'nt see anything so... ), a new GPU coming up!!!

Click to expand...

Sorry to hear that. Please let us know if another (good) video card does the trick!

- Nick