Screen Savers and Firewire Drives

For some time now I've had an odd problem on my MacBook wherein my Time Machine firewire drive appears to spontaneously, and without reason, disconnect. No warning is produced, no error message appears. It always happens, in fact, when the computer is not in use. I leave the system on, say, while a large backup is taking place, and I go up to go to sleep. I come down the next morning to find the drive unmounted. The only sign something's gone wrong is an entry in my system log that reads something like this:

May 10 11:01:02 mrpooter[255]: Stopping backupd to allow ejection of backup destination disk!

Weird, huh? I know!

My Energy Saver setting are set to never sleep the machine and never spin down hard drives, though I've tried every variance of this, as per this Apple Knowledgebase thread, to no avail. The problem persists.

After reading that thread, though, I was able to narrow and eventually solve the problem. Oddly, it seems to be related to my screen saver. I've been using an iPhoto album for my screen saver for a while, and I wondered if it had to do with that. So I switched back to one of the built-in, included screen savers — Arabesque, if you must know — and it's all better now.

For a few nights in a row now I've been able to leave my machine on indefinitely, even overnight. And where this would once have certainly cause my firewire drive to unmount, it no longer does.