You have noticed that the system logs in the C:\Program Files\Symantec\SharePoint\Logfiles\system folder have began to be filled with the errors for RTCommandService but the product appears to running correctly except for this error.
"2012-08-07 0:00:04","(null)","-1","Error","There is an error in X ML document (0, 0)."," at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle, XmlDeserializationEvents events) at System.Xml.Serialization.XmlSerializer.Deserialize(Stream stream) at Symantec.Sharepoint.Service.RTCommand.Service.GetEngineStatistics(ScanEngine scanEngine) at Symantec.Sharepoint.Service.RTCommand.Service.UpdateStatistic(StatSourceId srcId, ScanEngineStatistics objStatistics, ScanEngine scanEngine, String spssMachine)","UpdateStatistic","RTCommandService"
The issue was traced to an issue in the C:\Program Files\Common Files\Symantec Shared\SharePointEngine folder.
Add / Remove and clean installation of the Symantec Protection for SharePoint Servers product resolved the issue and the error went away.