Same thing has happened to me, installed 6.1.2 OS and tried syncing - music will not sync and tracks reduced from over 6000 to about 10.
I've tried removing and re-installing iTunes
I've tried syncing a few songs and play lists and then the whole library. All music has now gone
Apart from that everything else seems OK although maine use of ipod is as a music player.
Steve Jobs must be spinning in his grave.
Facing a similar issue... but I am unable to sync music after updating my itunes... yet to update to new ios... reading these posts, i am not going to upgrade to new ios.... I had taaken a great deal of pain to rename and organise my library... will i loose all the track names, abum names, artwork etc on reinstalling my itunes???... i have not purchased any music from itunes... all were ripped and from my cd collection....
I'm starting to feel like I'm walking through a land mine every time I upgrade apples products these days.
I decided yesterday to "restore" my ipod touch 4g to reclaim space that itunes/ios seems to munge on its own from time to time. I was running 6.0.1 which, despite a simple bug, was usable and reasonably fast. I would have PREFERED to restore to 6.0.1 but itunes insisted on giving me 6.1.2... Ok, how much worse can 6.1.2 be from 6.0.1 I thought to myself.... They claim better performance and bug fixes.... Yeah right.
The good news is the wipe clean and rebuild with 6.1.2 gave me back nearly a gig of space, but the bad news is:
1) During the restore, itunes would stall trying to send the ipod apps, etc and the device would lock up and spontaneously reboot. It must have done that 20 or 30 times.
2) I cant trust the restore because it borked 3 attempts at restoring the apps and threw all kinds of errors.
3) I can't trust the music on it because it borked the music copy once and took 15 minutes "waiting for changes to be applied". Based on the device being locked up and spontaneously rebooting for the apps, I thought it was dead, so I'd keep resetting it / killing the sync and retrying. This was not working.
Being desperate for a functional ipod (as a device it's only purpose is a music player), I decided to let it go and it took nearly 30 minutes, for what I think was the ipod creating its database of about 11000 songs or so (I remember previous versions of ios would only take about 5 minutes or so).
Once it got past that hurdle, the actual music copying more or less went without a hitch.
I did a test play of one of the songs and it does sync again with itunes, but it took about 5 minutes for the "waiting for changes to be applied", which constitutes only a single 2 1/2 minute song being played.
Here's hoping a device reboot and second attempt will smarten it up.
Apple as a company appears to be have some internal issues that are preventing them from putting out products of the quality they used to put out when Steve Jobs was still alive and the problem appears to be getting worse and worse with every release.
What is a real shame is that nowhere is Apple is even bothering to address or even admit this issue. For a company that big, all it takes is a small tab on the website saying that users might be facing this issue and we're looking into it.
The ONLY two reasons I use the iPod is because the stupid head unit in the car supports it and that I control my Logitech Squeezebox Touch with it via iPeng. Other than that, the sound quality of even 320kbps or AAC ripped by myself from original CDs is rubbish. And no I don't use the throwaway earphones that come with the iPod, I have the Shure SE535.
I IWSH AND PRAY that the car stereo industry will FINALLY support flac. That'll be the day the iPod will be in the trash can.
OK PEOPLE IT SEEMS LIKE I HAVE SOLVED THIS
Connect iPod to iTunes (cable or Wifi). Select all the songs in your library and uncheck. Click on your iPod in the side bar. In the Summary page, scroll down a little and look for the box 'Manually manage music and videos'. Uncheck that box.
The box above it called 'Sync only checked songs and videos' will be automatically checked now.
Go to your music library = main iTunes window, select all the songs, right click and select 'check selection'.
Click on your iPod and click Sync. The music will start to copy.
Best of luck!