Hi
If it doesn't do it in safe mode it seems like a safe guess that it's related to your graphics card somehow.
You are running the same Graphics Card that I am.
What I always try (since I have no idea what's happening) it to log in it safe mode go to Device Manager select your Display Adapter and select Uninstall.
Then reboot your computer in normal mode.
This will force Windows 7 to find, identify, and re-install your graphics card and find what it thinks is the correct drivers for it.
This works a lot of the time for me.
If it doesn't, come back and maybe someone else will have another idea.
It's not impossible from the way you describe how it happened that the graphics card failed.
They don't usually just go black while...