I'm an amateur trying to do something very simple and very necessary and failing to get off the ground.

I've got a Power Mac G5 running OS X Tiger (recent upgrade from Panther) and Garage Band. I blew 100 bucks on an M-Audio Quattro to convert my guitar signal from a jack to USB signal. I can't get any guitar signal into my Mac at all. Nothing.

I had the latest Quattro driver for Panther, then got the driver for Tiger. The computer sees that the Quattro is there--I can select it as the input/output device in Utilities-Preferences and GarageBand Preferences. I can hear the guitar via headphones plugged into the Quattro (if I press the monitor button). But nothing gets to the computer.

I tried another freebie recording program, so it can't be a Garage Band problem. I've tried a preamp. I've tried a microphone instead of a guitar. Nothing gets from the Quattro to the Mac.

I exchanged e-mails with M-Audio tech support for 9 months and followed all their instructions--nothing. I mailed it back to them, they mailed it back and said "In our hands, your device works--you can't have a refund."

I have a Quattro that is a $100 paperweight, and I'm really mad. I just want to record a little music. I have a really really good computer.
What in the name of all that is holy do I have to do to get my guitar signal into my Mac?

Thank you.

-TJK