when you change the sticks, set your your bios to the fail safe defaults. it's looks like maybe your mobo isn't setting the ram timings correctly. are you getting the static out of your body (grounding yourself ) before you are messing with this?
run memtest86 from the cd. if your ram is ok, then maybe it's the mobo
run memtest86 from the cd. if your ram is ok, then maybe it's the mobo