Hello and welcome to TSF.
I just wanted to make a couple of recommendations. First off, your EVGA 7800GTX is covered by a lifetime warranty so you should do an RMA to get it replaced.
Secondly, even if your PSU is not the problem right now, you should go with your instincts and replace it with the TS750. The BFG 650w is a terrible psu. There have been several issues with them posted here and a friend of mine had one take out his motherboard and RAM when it died. In fact, I had bought the same unit, but after seeing a couple of threads here involving that power supply and reading JonnyGuru's review on the unit I replaced mine with a Trio 650. I also informed my friend (who had recommended the PSU to me) of my findings about the quality of this overpriced, Topower built unit. About two weeks was when he called to say his system was dead.
Anyway, enough scary stories....
Just thought I would throw in my two cents worth and now I'll leave you in Manic's capable hands.