I have tried adding two different DVD drives to my Mac Pro and both of them have the same anomaly. This only happens in OS X, not when I boot into Windows 7 x64. This is in the bottom bay. I still have the original superdrive in the top bay. 1. The computer will not go to sleep automatically. I can however make it go to sleep from the menu. 2. The drive appears to make a periodic noise. It doesn't sound like its trying to spin up but instead like it might be trying to move the head to the inside/outside. 3. Putting a disc in the drive causes all the above problems to go away. The ASUS drive made a really loud noise when it was doing this. The LG drive is barely audible. This only happens in OS X. When I boot into Windows 7, it works fine, so it is a problem with OS X. This computer has the single 3.33 GHz hex core processor with 6 GB of RAM. Has any one seen this before?