Hi guys, I receive several blackscreens after rebuilding my PC. Its running on Win7 64bit and my line up is this one:

Mobo: 870 c45
Gpu: 4870 Ati Radeon (sapphire)
CPU: phenom 965 3,4~Ghz
PSU: Chieftec 500s8
RAM: Gskill Ripjaws two sticks @ 4GB

I get blackscreens, when alt-tabbing (even on desktop without any applications running), PLAYING more older games like WoW/LoL andmoving the cursor into the TASKBAR to switch between e.g. browser windows.
Strange is, I neither get errors in Blendtest95, Memtest86+,GPU-Z and strangely NOR in battlefield3.
I tried several things before i decided to steal your time: Reinstalling Windows,drivers,drivercleaner in safe mode, starting with 640x480 and install drivers than, switching windows from energy effience mode to maximum and taking out my pc components.

Last but not least my gpu has two lights on when blackscreening d601, d1601, but honestly I THINK its not a gpu problem (it WORKS with bf3 not with alt-tabbing? wow). I only swapped ram/psu/mobo and the blackscreens occured.

THANKS <3