I've had my 4G iPod and iBook for about 6 mos. now. Just two days ago my iPod would not mount in iTunes or Finder, but I could see it in Disk Utility. I ran disk repair, and it found a couple of errors but fixed it right away.
I then went to iPod updater and restored my iPod, which reset it to factory settings. It then mounted in iTunes and restored the music without any problem. I think I rebooted after the restore but I can't remember, restarts never hurt IMO.
Oh...and it's possible that dropping my iPod a couple of feet to concrete cause this problem. hee hee, but it works fine now...a tribute to Apple's quality products.
Since it's new, have you checked for the updates in firmware, etc.???