I've had problems syncing music from iTunes 10.5.
I can sync some music fine, but then it randomly gives up the ghost and decides to say that some audio files cannot be found (usually, this is most of the audio files), even though my iTunes Library is consolidated and all file paths are correct and unbroken.
Then, it decides to re-sync all these unsynced music items, but classify them as 'Other', rather than 'Music', meaning they can't be played or even accessed from iPhone (which is iPhone 4, by the way!).
Then it decides it would like to re-sync all the music that had originally been synced perfectly, converting them to file type 'Other'.
All in all, this means I can't sync any music to my iPhone, because it just fails. All the music that can't be synced/is classified as 'Other can't then be deleted from the phone from within iTunes because iTunes doesn't recognise it as being synced in the first place, leaving me with GBs and GBs of space taken up by 'Other' on my iPhone which has to be completely wiped and restored to regain the space.
Anyone else experienced this?
Yes, I had exactly the same. I did another restore and then only transferred selected songs at a time. ie. didn't set 1 transfer going and then add to it. All ok now.