I have a 2.66 macpro with three internal drives. I use one drive for time machine. When the macpro wakes from sleep the hd with the time machine backups on it doesn't always mount. I have to shut down and restart the macpro. I have swapped the hard drives to different bays and I have swapped between two hard drives for time machine use. When I woke the macpro today the hd with time machine backups on it didn't mount. It took 4 restarts to get it to mount. I have repaired permissions and I have run disk warrior. I have now turned off time machine and am using superduper for backups. I have a mbp and use an external drive for time machine backups. This works flawlessly, plug in drive, Tm backs up, unplug drive. I'm wondering if I should get an external drive for time machine backups. Is there a problem with macpros using internal drives with time machine? It's a pita !!!