I have a new exchange server and am currently in the process of slowly moving mailboxes from an older 2003 exchange server to the new one. Everything seemed to be goign just fine, but every so often I get issues with ActiveSync and sometimes OWA. I also will randomly get errors when opening user mailbox properties but only when I select specific tabs (such as the calendar settings)
With all the items above (and it probably shows up in other places), I get an error, on screen (EMC), on a web page (OWA) in the event log (ActiveSync):
"Operation not valid due to the current state of the object"
For active sync, error code is 1309