Mom can't log into PC. Started about same time as 19.6.1.8 update

My parent's called my this morning and asked me if I could figure out why they couldn't log into my Mom's PC (Windows XP Media Center SP3).  It would start to log in and then log out.   The PC was also very sluggish when booting up and shutting down. 

 

I did some searching and the only things I could come up with are http://support.microsoft.com/kb/555648 and http://support.microsoft.com/kb/892893, both which are supposedly triggered by having Malware installed at some point and then removed.  She has NIS 2011 installed and doesn't run and install any programs so I don't see how she could have any malware on her machine that suddenly got removed. 

 

I was very puzzled what could have changed since yesterday, when I decided to reboot my PC and noticed that NIS 19.6.1.8 installed.  My PC (XP SP3) got sluggish as well, though I could log in without any problems.  Is it possible that the upgrade to NIS somehow corrupted her Windows registry?  

 

Unfortunately, while I live relatively close to her, it's not close enough that I can just pop by and see if I can fix the problem.  Is there something she can do herself to try and fix it?   May Dad has a Windows 7 laptop which is working fine.