Yea, oddly enough trying a different USB port worked for me on a few occasions. Doesn't make much sense, but hey, if it works...
Erm, I can't try a new USB port, my laptop only has 2 and one got broken two years ago.... Tomi said something about a driver (de?)fault, is there any setting or something I can change?
This happened to me also, it seemed to fix itself after a while. Argh sorry that's no help to you right now though =[
I'm going to the apple store to see if there's someone there who can help, I doubt there will be, seeing as it's probably a problem with Windows and not my iPod.