Interpreting memtest results

I've been experiencing some crashing and BSOD so I'm testing my RAM. I have two sticks of RAM (2GB each). I ran memtest on:

Both sticks: lots of errors within the first hour
Stick A: 21 passes with no errors
Stick B: 13 passes with no errors

How should I interpret this? I kept sticks in their original slots when I tested them alone.

Thanks!