I also have the Evga 680i LT mobo, and I am experiencing the same anomalies. It has been flawless for 3 years, I have swapped out everything but the mobo, new cpu, gpu, memory and never a hiccup until now. I know there were numerous concerns early with many boards in this generation. I am not in the market to upgrade to an I7 system, so I too am looking for suggestions.
evga 680i lt
evga 8800gtx sli
8 gig corsair 6400
WD 320g HD
I have a 680i with a Q6600 processor. I was experiencing the same lock ups and graphical glitches in games. I am using SLI enabled RAM which has an "auto-overclock" feature. I discovered that disabling this feature in the bios solved my problems although the bus speed on my ram is now set at 800mhz . Anyways, I now run all games at near max settings and have not had one single forced reboot since I changed the setting. Before I changed it, I had to reboot at least every half hour.
Also, I discovered this work-around reading many forum posts like this one. These 680i motherboards are flawed and if I were you I would try clocking down your RAM even if you aren't using the sli-optimized modules. Can't hurt to try right?