Currently Being ModeratedMay 28, 2012 2:48 PM (in response to iBozz)
Well, eventually I had to go to the Level 2 (or whetver they are called) AppleCare geeks to get this resolved, as the "normal" guys couldn't resolve it.
After much "try this ...", "try that ..." and "try the other ..." they narrowed the problem down to a corrupt Address Book Group header in my iMac's Address Book.
It appears impossible to find out just which of my 55 Group headers was corrupt and the only way around it was to export all Contacts individually as vCards, dlete every Group and individual card entry in the Addreess Book and reimport all the vCards - and then somewhat tediously recreate all my Groups again from scratch.
It took around two and a half hours on the phone to AppleCare and forever to recreate the Groups, but at least it solved the problem!
Whether this helps anyone else i cannot tell, but if you have a bizarre syncing pronblem it might be worth looking at this as a solution.
But take my tip: before embarking on this, make an entry in the Notes section of each card so that you know to which Group or Groups a card belongs because it was a feat of memory way beyond me to remeber all of them and I still have the odd orphan in there awaiting a home!