the XMS3 run at 1.65V and the Vengeance run at 1.5V.
you are not trying to run both memory types at the same time, are you?
So the system works fine with the XMS3, right?
Do you have any memory values manually set in the BIOS or is every thing set to auto?
Have you tried to reset the BIOS after plugging in the Vengeance?