http://www.tomshardware.com/community/profile-992934.htm
Ok, this is what comes up for me when I look up your model number: http://www.techsupportforum.com/forums/f210/help-with-n...
These are the specs, according to that thread:
"12Va --- 16A
12Vb ---18A
12Vc ---12A
12vd---10A
5.08v----16A
3.3v ----15A
5.08Vsb ----2A
-12V ---.3A"
If the power supply genuinely has four separate 12V rails, then that could be your problem; perhaps you're overloading one of them. Or maybe the PSU is failing. Sometimes PSU manufacturers claim that there are separate 12V rails when there really aren't. Dunno.
Hope this helps from a previous inquiry.