also have a message;
'iTunes could not back up the iPad because the backup could not be saved on the computer'
Check this apple article out -> http://support.apple.com/kb/ts2529
Im not sure if it will fix that first thing, but it mentions the exact error in your second post.
I have just updated itunes to 10.2.2 and ipad1-64mb 3G- to iOS 4.3.2 on an intel dual core Mac 10.6.7 and I can't sync now either. Itunes hangs during the sync process when synching. I've had no issues with previous itunes versions or ipad iOS versions. Is there somewhere official we can report this issue?
I am having exactly that problem too, as described by tonethestone on 20 April: sync starts, backup gets 90% through then freezes, (resulting in a need to force quit iTunes when "not responding") and either I get an error message that iTunes "could not back up iPad because an error occurred" or " a backup session is already in use."
I am on iOS 4.3.3, syncing with iMac 21"; I'll try eliminating the photo sync, as someone suggested - I only have 99 on there.