Troubleshooting Black Screen, where to start?

[sk3d]

My rig has been working all fine but the electricity was cut and when i rebooted it wanted to recover windows.. didnt really read what would happend but i had to install all the things once again.
After this I also tried to install one more 5830 because i had got my extender, but i couldnt really get it up running stable so i removed it, the soldering on that 16x extender was really crappy :S

Now my rig isnt stable, it works a couple of hours and then gets blackscreen.
2*5850, 1*5830
850W
Windows 7
Catalyst 10.11, 2.1 SDK

Is there anyway i could troubleshoot whats shutting my computer down? Which component dies, etc

[1714103763]

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[1714103763]

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[1714103763]

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[1714103763]

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[Roland68]

try without overclock it ...

I had the same with primary card memory underclocked ...

was too much ... and black screen ...

[sk3d]

But now the last time i did just overclock it a bit, not much.. it was far below the clocks i had when it worked all fine :S