A lot of the 790i Ultra boards are having problems with freezing under almost any load!
I've got one with twin 8800GTX OC's in SLI, and it was freezing both with and without SLI. It was freezing in Win XP Pro and Vista Ultimate, both 32 bit versions. Sometimes it would freeze up solid when gaming or using the TV tuner, and sometimes it would freeze just sitting idle.
I RMA'd the first board and I've got the second one in and running, and it's starting to do the same thing. It seems to be less frequent, but it freezes up even with everything running at stock speeds.
If it keeps it up or they don't find a fix soon, I'll be asking for a third board. On the EVGA forums, there are plenty of people who are on their fourth and fifth boards. Many, perhaps even most users don't have any problem, but from the EVGA forums and other board makers forums, it's a sizeable number of the 790 boards th at are having trouble.
There are an almost uncountable number of solutions posted, but most eventually start having the problem again.
The best guess of everybody is that it's a problem with the nVidia chipset, and not the individual board makers.
I guess they also had problems with the early 680's and 780 boards. The computer is fast as hell when it's running...., but without warning, it'll just freeze solid. The video and audio just stop and it doesn't respond to any inputs from mouse or keyboard. All you can do is push the power or reset button and reboot.
It'll start right up again and run fine for perhaps a couple of days, or perhaps a couple of minutes, and then do it again.
For a high-end board, it should at least be rock stable at stock settings!