captainsmiffy,
Are you synchronising to Mac or Windows ?
Just because I'm thinking that if you are able to replicate this problem, then it might be time to start looking at crash logs. So I'd like to try to point you in the right direction as to where to look on your sync system.
If we're able to isolate it reasonably confidently as a technical problem with the Apple software (rather than some issue with BT), then I'll be happy to log it on Apple's Bug Reporting system for you.