I was having the same problem with my iPod that everyone was describing, where I would update (sync) my iPod with my updated music library. Disconnected from winamp and would go to listen to some music WITH my iPod only to discover, there are "no artists".
Sure enough, the data is physically there, shown by the only 50 GB or 160 are free...
Puzzles, I began reading, I stumbled upon this forum and thread, reading up and down trying to figure out WHY.
I discovered something very interesting that I hope will help all of you, but It may seem strange. I tried plugging my iPod in to do some trouble shooting one day and with much disapointment, I accomplished nothing, until out of pure frustration I unplugged my iPod abruptly, without using winamp or windows 'eject' feature. BINGO, files are back... I can now browse all music files, and sure enough they all play, nothing corrupted, all syncd files are there. PERFECT. I was then curious...
I pluged my iPod back into the computer, then using the 'eject' feature (first with winamp, then windows system tray) recreated the same discrepancy, to a T. My solution... as dumb as it sounds. Don't 'eject' my iPod ever. I just yank the baby out. There is clearly something wrong with the 'eject' function, and it messes with the file system, as EVERY time I use the eject feature (not only are the files not visible), when I go to plug the iPod back in windows suggests that I run check disk to find errors on the storage device, I just cancel and open winamp, then rip the sucker out before I 'eject' I think when you open your iPod up into Winamp it seems to fix itself and works just fine (ive tested my theory several times)
I hope this helps atleast 1 person, Thanks guys