backdoor.tidserv gone but not gone

Hi.  I have Symantec Antivirus 10.1.6.6000, virus definitions 11/03/09 rev. 3.

 

In the last two days I have seen auto-protect pop up with Backdoor.tidserv something like 12 times.  Each time it says, "cleaned by deletion."  But then a few hours later it comes back.  It seems there must be some part of this infection not being removed.  I have the risk history log that just shows the dozen occurences I mentioned and a cluster of trojan horse files that were supposedly quarantined on 11/8/09.  Can anyone help?

 

Thanks in advance.  Apologies if I have omitted some baseline information.  I have never posted to this forum before.