When you get this error you should see the following event in the event viewer on the Exchange server.
Event ID: 1008
Source: MSExchange ActiveSync
An exception occurred and was handled by Exchange ActiveSync. This may have been caused by an outdated or corrupted Exchange ActiveSync device partnership. This can occur if a user tries to modify the same item from multiple computers. If this is the case, Exchange ActiveSync will re-create the partnership with the device. Items will be updated at the next synchronization.
Solution:
Make sure the user who is trying to connect with his phone has the option ‘Include inheritable permissions…’ checked on.
(Active directory -> right click the user -> properties -> security -> advanced -> ‘Include inheritable…’).
Note: If you don’t see the option ‘Security’ go to Active directory -> view menu -> check ‘Advanced Features’.