MA stopped-extension-dll-exception

Our Identity broker MA is failing on its Delta Imports with the ever helpful "stopped-extension-dll-exception" error.

From Event Viewer, I get:

The extensible extension returned an unsupported error.
The stack trace is:

"Unify.Product.IdentityBroker.LdapOperationException: Error during processing of SearchRequest targetting cn=changelog: Operation timed out while waiting for message queue with id of 10. ---> System.OperationCanceledException: Operation timed out while waiting for message queue with id of 10.
at Unify.Product.IdentityBroker.LdapConnection.GetMessage(Int32 messageId)
at Unify.Product.IdentityBroker.SearchRequest.Send(Func`2 send, Func`2 recv)
at Unify.Product.IdentityBroker.LdapConnection.SendRequest(ILdapRequest request)
--- End of inner exception stack trace ---
at Unify.Product.IdentityBroker.LdapConnection.SendRequest(ILdapRequest request)
at Unify.Product.IdentityBroker.LdapConnectionProxy.<SearchRequestPaged>d__8.MoveNext()
at Unify.Product.IdentityBroker.ImportProxy.<GetChangedEntriesPaged>d__30.MoveNext()
at System.Linq.Enumerable.<SelectManyIterator>d__14`2.MoveNext()
at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
at System.Linq.Enumerable.<SelectManyIterator>d__14`2.MoveNext()
at Unify.Product.IdentityBroker.ExtensionMethods.Take[TSource](IEnumerator`1 source, Int32 count, IList`1& items)
at Unify.Product.IdentityBroker.ExtensionMethods.<Page>d__3`1.MoveNext()
at Unify.Product.IdentityBroker.ImportProxy.Import(GetImportEntriesRunStep importRunStep)
Forefront Identity Manager 4.3.2266.0"

Apart from the fact that there was a dll exception, any idea what this is about or where to look for more useful information? I am seeing nothing with any errors in the IdB logs.