I have a newly installed 850w Kingwin P/S that replaced a 500W and the 350W that I was using to power the 5830. System seemed to be stable, going 7days + without a hiccup, but now seems to lock up (screen frozen, or blacked out when I turn the monitor on) at least once a day (of course, usually just after going to bed, or leaving for work).
Looking for some ideas on what might be wrong. Dirty power? [...] Just frustrating to have a system that ran so well becoming such a PITA.
I would seriously consider dumping that kingwin psu. they are junk. the fact that its worse with this psu (as opposed to your 2 psu setup) should tell you something.
you are getting pure lockups right? nothing in the event logs? thats another indication its bad hardware, not a driver issue.
lower clocks = less power draw from the psu of course, and less voltage swing on card loading/unloading (on a junk PSU that is, real ones have no problem). could be another reason milder clocks give less chance of lockups with your current setup.
for a serious psu (one that delivers its rated power, cleanly, and at real world temps), get an antec, pc power and cooling, corsair, seasonic, or silverstone.