I just had the same problem but solved it pretty quickly and easily. I think it was caused by not properly shutting down the entire system before doing anything with my external firewire box (canopus box). To solve this I shut down the computer, unplugged all firewire devices (external drives & canopus box) then restarted the computer while resetting the P-Ram.
– to reset P-Ram hold down the P,R, Command, & Option key all at once while restarting the computer. Wait for the computer to make the startup BONG sound at least 3 times before letting go of the 4 keys.
Once I had reset the P-Ram I trashed the Power Management P-List File. You can find this file here.
MAC HD -> Library -> Preferences -> System Configuration -> Power Management P-list file
After that was trashed I emptied the trash, shut down the computer, plugged my firewire devices back in and started up normally. Everything works fine after that.
Hope this helps,
Pete