Norton SystemWorks 2007 (Standard) - WinDoctor won't execute

I run Norton SystemWorks 2007 (Standard) along with NIS 2009 on a PC running Windows XP SP3.

 

 

Last week, NIS correctly identified and blocked Trojan.CDur.  My computer was not infected; it was quarantined and removed.

 

Since then, I have been unable to run a Norton SystemWorks scan using WinDoctor.  It will not open from either the tasks > find and fix problems menu or from the SystemDoctor warning box (the one that warns users that Windows problems have been detected). 

 

I have been forced to use One Button Checkup to fix any/all problems in Windows.

 

I'm not sure if the problem is related to the blocked Trojan.CDur or if updates to Windows XP are causing this headache.

 

How can I fix WinDoctor so it will run again?