okay, now that makes much more sense....you are only having the problem when the new ram is in...one stick or two. gotcha. the example post confused the **** out of me, to be honest lol.
what voltage are you running the ram at currently?
if it is stock, probably like 1.8V.
try turning that up to 2.1V
there are several xms2 ddr2 800 availible, and even though they "should" work at stock volts....doesn't mean they will.
post back, i am interested to find the solution to this.