zach,
This is a well-documented problem in the last month - tons of posts on the iPod discussion boards at Apple. Many folks are attributing it to something in the last iTunes update, but a close friend who keeps everything up to date on his Mac has not experienced the problem - while I can't get my shuffle recognized by any of my computers (4 Macs and 1 PC). The iPod refuses to mount, nor is it recognized in iTunes. I've attempted all fixes without success. I finally filled out a repair request on Apple's website as it was still under limited warranty, expecting to pay the $29.95 shipping/handling fee. Instead, within the hour I received an email from Apple stating they'd be sending me a new shuffle at no charge (as long as I shipped back the non-working shuffle). Don't know how long you've had yours, but I'd drop Apple an email and see what they say. There are a bunch of unhappy shuffle owners out there at the moment; maybe Apple's starting to do something about it...
- vickster