What is the BSOD error code? you know teh STOP 0x0007fb....etc, that would be the first thing i would investigate, then also have a look in the windows events viewer.
Also you say that with one stick of memory it works: is it always the same stick of memory that works fine?have you tested both individually with memtest for a long time?Did they comeas a pair?And have you set the timmings and voltages for them in the BIOS correctly?
Also what OS are you using?
At teh moment I don't really think you can say it's the motherboard at all.