Sei:
Don't sweat, you just need to re-register your iPod as a removable drive. Here's what to do:
1. First, reboot. It's just a good starting point.
2. Open up the iPod Software Updater. That's the tool that shipped with your iPod that you use to update or restore it. Just open it up. Sure, it'll say that no iPod is connected, that's okay. The important thing is that this program "polls" your system for an iPod, so that when you plug in, it'll see it, and "catch" it.
3. Plug in your iPod. It should behave normally. If it does, close the software updater, dismount your iPod (via the system tray icon), unplug, and plug back in to make sure that it'll "catch" again.
4. If it fails any part of step 3, you'll need to put your iPod into "force firewire" mode. Hold down the Previous and Next buttons on your iPod for about 7 seconds. The screen will go to the "checkmark" screen, even if you aren't plugged in. Now, start from step 2 and see what happens. If it catches properly, close the updater, dismount the iPod, unplug, and reconnect. It's worked for me in the past.