I would try shutting down the PowerBook, take out the battery, and let it sit for five minutes -- this flushes the volatile RAM. Then reboot. Another suggestion is to wipe the PRAM: reboot and hold down Option-Command-P-R while booting (before you see the grey screen) and until the login screen comes up.
You could install the DevKit that came with OSX, it has a program called "USB Prober" that lets you peek at what exactly is getting transferred via USB. You may also want to check Finder for the file "IOUSBFamily.kext" which is in "YourHD/System/Extensions. It should definitely be there, but you should try checking it's permissions by clicking it and hitting "command+I". At the bottom of that pop up window it should say "Read Only". Click "Details" and the owner should be "System". If the permissions are incorrect, repair them using DiskUtility.
Hopefully this will do the trick. :mac:
