I'm on an early 2008 mac pro - used to be on a Powerbook G4. I have a 300 GB LaCie d2 Extreme external HD connected via firewire 800. Both are in 10.5.2. While on my powerbook, the drive behaved normally - fell asleep after no use, then awakened when I needed to access something. On my new mac pro, the drive behaves strangely. I only use it for backup, so it's only accessed once a day. The rest of the time I do not use it. When it's not in use, the drive sporadically wakes and sleeps. I've tried to pinpoint the cause to no avail. I've tried all the usual suspects: browsing the forums, checking the "hard disk sleep" preference in energy saver, switching the firewire 800 cable with usb and firewire 400, watching activity monitor to see if there's a program accessing the drive (haven't found anything, but that doesn't mean it's not there). None of it works. Suggestions, anyone? Thanks for your help. Cheers!