A bit of background on this one.
When migrating the Fublic folder would not move so a new one was setup on the 2010 box EX1. I had some trouble with the OAB not syncing this was eventually over come by changing some the aliases for some distribution lists to not have spaces :sigh:
However the free busy folder on the 2003 box will not sync with the new one created on the 2010 box.
Pic of error message attached.