We need more info.
What OS version?
Whats the configuration of your USB devices? As in, what goes into what port?
Your drive is FireWire - your scanner is USB right?
They shouldn't have anything to do with each other.
Check that the FireWire drivers are the latest.
Start up the computer with only the Que! and the keyboard/mouse plugged in.
If that doesn't work shut down for 10 mins and unplug everything, then try that.
Does the Que! work if the Canon is unplugged?
Try the other FireWire port.
Um... Make sure you're running OS 9.1.
Zap the PRAM.
I can't really help without more specific information...
Cipher13