Two daughters, a son-in-law and the mrs - every one of them has had the same problem at one point or another, sometimes two or three times. That's with iPhones 3 & 4, iTouch, current iPod classic and two different generations of iPod Nano all on different computers (including one mac). Ipods are great pieces of hardware, but iTunes is utterly crap software. Make sure you take backups of your files and either:
a) Don't upgrade iTunes; or
b) Try one of the iTunes alternatives that are around - google it.
My own solution is MP3s, an Android phone and a whacking great micro-SD card. No problemo...