I had trouble with SE sync on Friday with my son's phone, he has my old C902 and I forgot to delete the sync so he ended up with all my contacts and all his. Anyway I wanted to set him up with his own sync account and then edit the contacts to get rid of mine. The system kept going down or not completing or losing the page on the internet side of it and on the phone it failed a few times - grrrrrr! After much persistence I got there in the end but it took a lot more effort, refreshing and resyncing than normal.
So in short I would say keep trying... their system is 'quirky' and that is being kind!