I have an iPad 2 with iOS 6.0, and iTunes 10.7.
I'm trying to copy music from iTunes to my iPad. Everything seems to act fine, but it doesn't actually copy the music. If I select the destination playlist on the iPad, it lists the tracks, but they are greyed out with a stationary grey sync icon to the left. iTunes does not show any activity in the top area.
It is set to manually manage music, my iPad is registered with the same Apple ID as iTunes, and my iPod touch is set up in a theoretically identical manner yet I can copy music to that. Telling my iPad to sync does not have any effect.