If you experience Exception Error 1222 Severity 16 State 18 with the SPID being less than 50 and the LoginName shows 'sa', then these may be generated by the GhostCleanupTask.
To verify if indeed the GhostCleanupTask is the cause, try add the EventClasses 'Exception', 'Lock:Timout' and 'SQLTransaction' as well as filter on the LoginName 'sa' in SQL Server Profiler.
As mentioned in this link http://support.microsoft.com/kb/920093 the below will stop these errors:
DBCC TRACEON (661,-1)
To re-enable the GhostCleanupTask use:
DBCC TRACEOFF (661,-1)