Powermac G5 Graphics Problem

Ok, so a few months ago i ran into a problem with my graphics card..

here is a screen shot.. After posting i was told it was most likely a graphics card problem.. Picture below of the original problem.. This suddenly occured after awakening my computer..
VRAM specs then: RADEON 9800 PRO 128MB



So, do to funds being low i borrowed a friends graphics card for a little while.. Might i add i had absolutely no re-occurance of the problem at all.
VRam Spec: NVidia GeForce FX 5200 64MB

After finally being financially stable enough to get a new card i did.. I bought a re-flashed Nvidia Geforce 6200 256MB..

Everything is going just fine at first.. then after sleeping my computer randomly i get a similar to problem to before.. Just not half as bad and a little different..




^Note the above screen shot was taken after exiting preview while trying to edit out my name (Explaining the double dock)... After having opened a video file in itunes and then hiding itunes.

This problem will also happen sometimes when i open a new video file or something like that.. This is very random and almost always happens after being awaken..

Now, the weird part.. I simply log out, log back in and everything is back to normal..

Any suggestions, past experience etc would be appreciated..

I'm leaning away from getting yet another graphics card especially since i just received this one last week after waiting for three weeks for it to be shipped from Australia.. The ebay auction said its a new card and has been tested etc..

A link to the auction is as follows:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWNX:IT&item=260284030362

thanks.