I've got a bit of a pattern on my systems that don't have optical media drives. Most of them (not all) and across several models (Dell), produce the following error in the service errorlog.txt and display an error for the CD on the individual system webpage.
System.Management.ManagementException: Provider failure
at System.Management.ManagementException.ThrowWithExtendedInfo(ManagementStatus errorCode)
at System.Management.ManagementObjectCollection.ManagementObjectEnumerator.MoveNext()
at Lansweeper30.sweeperthread.GetWMI(String Querystr, String Table, clsComputer mycomputer, String section, clsThreadinfo Threadinfo, SqlConnection& sqlcon)
Everything keeps working, the service doesn't crash, and the rest of the scan information is complete.