Same thing here. My feeling is a overheated CPU. I first installed the heatsink that came with the CPU. Everything ok until I try to play some video game. The MoBo was giving me a warning about CPU get hot. I changed to a "supposedly" good cooler (ZALMAN ZF9225ATH) that it didn't do the work at all because my previous AMD Athlon 64 X2 (twice, at that time I thought it was the MoBo) and now this FX-8120 giving me the exact same problem (first PC freezes, then I couldn't boot it, NEVER again) Thanks to (and I have no doubt by now) that cooler piece of shit.