Weird DVD Drive

8 Custom built computers; all identical parts.

1 DVD drive will not boot when it's in the case. It will boot when taken out of the case and laid on the counter. Tried another dvd drive that is working, and it did the exact same thing.....works fine outside of the case, but will not work inside the case! There is not normally anything that could cause a grounding issue on the computer case or the case of the DVD drive. It would not be a bad data cable because it works laying outside the case (using the same cables)... it would not be motherboard because it works outside the case.... what could it be?

It ended up that we tried another molex to sata adapter for the power cable, and it worked! Either both of the SATA power cables coming straight off the power supply are defective, or we have a defective power supply. The power supply tests good, and both of the SATA connectors on the powersupply test good on a tester.......