Screen Crashes - becomes unreadable

Hi guys,

i recently loaded Vista Ultimate 32 and SP1 as well as my Xp pro install.
All went well except for that my screen suffers issues. That is when i try
and change resolution or set dual screens I get blue diagonal wavey lines
over the screen which you cannot see through. The only fix is to reboot the
PC. This also happens in games and occasionally when coming out of screen
saver. I have tried old drivers / new drivers and a bunch in between but end
up with the same result. the weird thing is XP is fine and all behaves like
it was meant to.
I have tried cleaning all drivers out and reinstalling etc but the problem
remains. Any ideas? My specs are:
E8400
G/Byte EP35-DS4
Nvidia 7950GT 512Mb Card
Silverstone 650W PSU
2Gb RAM
Vista SP1 / Xp Pro
Samsung 204b (1600 x 1200 native)

Any suggestions are appreciated as I am at wits end and Vista has really
become unusable :-(