Sick nVidia GF3

[Roy Hackett]

This morning the Cube woke up sick. Blocks of screen image were 
missing. A reboot produced another blocky hash of desktop.  I tried  to 
  reboot from my other fresh partition OS and thing got worse.  I loaded 
Disk Warrior and got a chopped up menu plus I could not eject the CD  
using the usual trick  of mouse down. A Shift reboot gave me the safe 
mode once only.
I pulled out the GF3 and put the stock ATI back in.  All is well.
So, how  do you get a video card fixed when nVidia has  no end user 
support?
Ideas?
Thanks, Roy