SPBBCSvc.exe memory hog

My wife is using Norton Antivirus 2006 on a Windows 2000 system.

 

Around the beginning of June, it started misbehaving: SPBBCSvc.exe grows without limit, eating up all the memory and making her system extremely slow.

 

It appears that SPBBCSvc.exe is a core part of NAV, so she cannot kill the process or even lower its priority.

 

Has anybody else seen this problem?  Any suggested fixes?