Patriot Signature Line 512mb DDR400

ok so here's the situation, i've just built my new rig and i'm testing things out to make sure its alll smooth, so i give memtest 86 its go, had 20errors by test 3, ok so its either a slot or a stick of ram, i start by removing the 2nd stick, still get errors, ok so i'll remove the 1st stick and replace it with the other stick, error free where it was erroring, so i put both sticks in (reverse of how i started) and i don't get those errors, so i took the stick out of slot 1 (the errorless stick) and run with the stick that errored in slot 2 and i don't get the same errors....just a freak accident or a reason to look into having the stick RMA'd?

*note that i didnt run the full test any of the time because the first there was too many errors and the rest i expected that the same errors should show up no matter which slot it was