Aftermath of a strange crash...

[Marthenil]

Alright, this is my second thread in the computer forum today, which cannot be a good sign :P
Anyways, long story short, I just came home from a long Xmass holiday. I played metro 2033 just fine, nothing strange, then some Torchlight 2,
After a while and because I wanted to avoid unwanted attention from some friends I switched Steam to offline and tried to run TL2 again.
This is where the shit hit the fan. The PC locked up for a few seconds and immediately restarted by itself. After restarting it would freeze at the windows loading screen forever (However the sound kept going, and I could even log in using the keyboard and even play music.)
After some hard resets I got a Windows failed to boot error and a prompt to use Windows repair, but nothing changed after I let it run.
Tried repair again, this time with the windows CD, and a System Restore. Same thing again. At that point I had no Internet con other than my non working PC
and thus no help, so I said what the heck let's try a format and proceeded to do so.
After the format everything seemed to be normal but after I installed the GPU drivers the same thing happened again. This is when it hit me that it was a GPU card failure or driver issues and proceeded to open the case to check things up. I removed it and put it back in and now works like a charm,
but this is whats bugging me: I THINK that one of the PSU 6-pins was slightly off before i removed it. Thing is I also did this with the RAM as well so I'm not sure if this is the issue as well.
Could the culprit be the slightly off 6-pin cable? Or would the GPU not work at all if the second 6-pin was not connected? What else could it be?
I noted the fact that I was away for a long holiday because the levels of humidity here are crazy. Could it be affecting the GPU or some other part? What can I do to get more info?
Some specs:
GPU: 660TI FPB by EVGA
MOBO: Asus P6T SE
CPU: Intel Core i7 920
Windows 7 Home Premium 64 bit
Feel free to ask for more info and thanks in advance!
EDIT: Forgot to add my PSU specs: Chieftech 650 watt (At this point I can't check for more info because I will have to reopen my case and
it will make some noise thus waking my GF but if it's necessary I will. It's a modular one.)

[vesseblah]

Could the culprit be the slightly off 6-pin cable? Or would the GPU not work at all if the second 6-pin was not connected?

Yes and yes. If the graphics card isn't getting enough power it would crash in the way you explained when starting a 3D accelerated program such as game. It could be also PSU or boot disc failing (neither of those like excessive humidity) but it's really hard to tell for sure.