I figured it out. Another thread about power supplies got me to thinking.
It was RAM voltage. The MB with voltage on auto had the RAM a hair below 2.5 volts, Kingsstons spec for these chips is 2.5 (+/-.25) volts. Remebering from overclocking that increasing voltages can sometimes help stability I took a shot. I tweaked the voltages to the high side of Kingstons specs (but still not not over) and I seem solid again now.
I had added another stick of RAM, but it didnt give me trouble right off (until I started fooling with video cards). It was the same exact manufacturer (Kingston) and part number as the other one, but was 1 year newer and had hyniz (sp) instead of samsung chips. I guess the newer chip isn't as tolerant of low voltages.
I have never had the trouble with SB cards others do, just lucky I guess. When I get troubles they are weird stuff like this.
(editted to add more detail for future reference of others.)