I would just like to say here that some motherboards are very picky about allowing dual channel operation.
I recently tested two 1GB modules (transcend 667) on a DG965WH, which would show up with errors in memtest86, MS memory diag. etc., but only in dual channel mode. In single channel mode, there have been no errors. I also manually reduced the timings to 5-5-5-14.
Mind you, someone who may not have tested the RAM maybe would never realise it had errors, because it easily performed all the tasks thrown at it.
I guess if anyone here owns any 965 series board, you might wanna test your RAM compatibility and timings. Sometimes errors show up due to wrong timings, or other incompatibilities like using single/double sided RAM.
The sad part is that hardware dealers will not replace your RAM sticks just because of certain errors in certain configurations.. all they see is that "windows boots up just fine". Many of them dont even know about memtest.