NIS2011 regularly disables antivirus and wont fix itself

We have several Dell Latitiude notebooks with NIS 2011 installed.

 

Over the past 6 months nearly all have at some time experienced this problem, some more than once.

 

I hoped version 18-5-0-125-EN  would fix it but it hasnt.

 

The only solution each time is to Uninstall and Reinstall NIS2011

 

See attached screen shot.

 

http://img703.imageshack.us/i/nortonagain.jpg

 

Anyone else having this problem?

 

Thanks