Cycling between MU patch loading (splash screen) and empty patch

[Victord]

Hello everyone:
problem started after normal shutdown/no edits/additions. at first, stuck in initializing. no video output. i tried accessing bios but still no video and still stuck. reseated ram, audio card and every other plug i could see. after a few boots into support tools (usually error 31 and sometimes 14) i had system booting except cycles between mu loading (splash screen) and empty patch. starts about a second each and after left on a few hours 'loading' extends to about 6-7 seconds. cursor is visible on splash screen and responsive. when empty patch is showing, can click on anything with pointer or use front panel controls but i'm not fast enough to try loading another patch or do anything else. I've cleared cache repeatedly. this cycling thing happened a few months ago at an outdoor (winter) gig. i though it was the cold weather had a button sticking. can't remember if i powered down more than once, but when i came back a few hours after sound check, all was working normally.
any suggestions?
thanks