When this happens, it means that the sync engine is not communicating with the FIM Service. As suggested above, the first thing to check is that the versions of the sync and service components are the same. If they are the same, try going to 'connect to database' property page for the FIM MA and refresh the credentials, this often fixes this issue. You should not need to run IISRESET for this to work.
BTW, a way to verify that this working is go to the 'search requests' link in the portal after doing this. If it works, it should show numerous entries that shows deletion and creation of ma-data objects and the mv-object, as well.