OK, this is my own fault:
Got an A8N-Sli deluxe with 3800x2 (s939), 7800gtx and 7100gs in it. Used to run it from its stock 2ghz at 2.5ghz with no problems, but when the CMOS battery died and I replaced it, I never bothered taking it back up to 2.5ghz again and left it back at stock 2ghz...