I am experiencing the same problem. Not sure what details below are useful, but here is the situation.
iPad 3, 64gb wifi model
have been using it with no problems, sync regularly
recently upgraded to iOS 6
please note, this process took a long while and with repeated failures.
where I live there is a bad internet service and it took several attempts
after iOS 6 all seemed well
did a backup prior to the installation of iOS 6
all my apps, songs, etc seem to be still on the device.
Just prior to this, I had iTunes ask me which library I wanted to use. Never had that before. I have only one library.
I am the single user of the iPad and iTunes account. One Apple ID.
I have shut down the iPad, shut down and restarted my MacBook Pro. Plugged in the iPad and still no change. Begins to sync and then I get the message "sync failed to start"
I am willing to attempt a reset, though I have a variety of data on various apps I prefer not to lose (GoodReader for example). I know my Evernote, Dropbox, Apple notes and reminders will remain on iCloud.
1. Should I attempt a reset?
2. Should I attempt this from the iPad itself or from iTunes?
3. Should I first try a "fresh" backup?
4. What about doing a "restore from backup"?
Sorry to have several suggestions. I just don't want to muck it up with a single command.