Norton Internet Security 09 and Network Problems

Last week I upgraded my laptop (running XP) from NIS 2008 to Norton Internet Security 2009.  Since then I had a problem with my laptop seeing my network.  Laptop did not bring up ANY WIFI networks and when I tried to use a wired connection using the ethernet cable, I still could not access the internet.   I believe this may have happened after a Full System Scan had been run.  My network uses a Belkin Router/Modem using WEP128-bit security. 

 

AND I also had my mums laptop (running Vista) here and connected it to my network, everything running fine until it started to run a Full System Scan.  Then exactly the same thing happened.  At least I think it was the scan which triggered the problem.  Switched it on the next day after the scan, and it could not see any wireless networks (there are normally at least 4 round here) including my own.  Mums laptop works fine on her network in her home using a netgear modem/router (WPA security).

 

I called a local techy guy who has managed to get my laptop to work again after uninstalling wireless and wired network devices and then reinstalling.  He has also changed my network security to WPA.  BUT what is going on? 

 

IS THERE A SETTING I NEED TO SWITCH OFF IN NORTON TO STOP THIS TOTAL FAILURE OF ANYTHING NETWORK-RELATED HAPPENING THE NEXT TIME I RUN A FULL SYSTEM SCAN OR WILL CHANGING THE NETWORK SECURITY HAVE SOLVED IT (if, indeed the system scan and the network security are the problem).

  

I want my PC to be secure but preventing any attachment to the internet is probably going a bit far!!!

 

Thank you