Try running your chips 1 at a time and testing. If they all run fine individually but not in certain combinations, it's probably a conflict or compatibility issue. If it is, sometimes you can fix it, sometimes you cannot. Try some of the things that G)-(osters recomended and also try diffrent placment of the mem modules in the slots (not sure what your mods are or how many slots you have). If the memory modules are not matched, or even worse, are diffrent brands, speeds, and or latencys, check your motherboard manual about what configuration (if any) can run them all single channel (not sure if that is possible with three chips, I guess it depends on your motherboard). Also, if two are matched, double check that they are the ones in a dual channel config and the third is running by itself.