Reason: Collection was modified; enumeration operation may not execute.

http://social.technet.microsoft.com/Forums/en-US/sharepointadmin/thread/d2d0e939-2e29-462e-a2f0-6f5e54f6e8fd

http://mysharepointofview.com/2009/10/synchronization-for-shared-services-provider-failed/