Canon software can be troublesome - Assuming you have checked all the connections and not using a USB hub - Firstly, delete any preference files relating to the Canon software. You can find these files by typing 'com.apple.<app name>.plist' into the search box of the Finder window. When you find the file just drag it to the trash, empty the trash and restart your computer. NB: ONLY delete files with the extension '.plist'. This is the preference file and can be safely deleted as the first step of rectifying any troublesome app.
If that doesn't work, delete and re-install 'ALL' the software on the disc that came with the scanner. I've always had better results installing all the software that comes with the scanner or printer rather than just installing the specific scanner/printer app on the disc. It's a simple enough task to remove any unwanted Canon files or Canon applications after installation.
Also, I noticed you are running Panther. If the scanner is new you 'may' have to get a previous version of the driver for Panther. Go to their website and check for Panther drivers.
Let us know how you get on.
