NIS 4 - Firewall crashes continually trying to configure blocking

I am running NIS 4 on an iMac with Mac OS X 10.6.1.

 

I recently wanted to add some XXX blocking info to the firewall.

 

Login in as an administrator

 

So I open Norton Firewall.

 

Click on the Firewall settings side tab.

 

Click on Connection blocking "Configure" button.

 

...it just crashes and writes a crash dump (as I can see via the Console application)

 

This happens relentlessly, so I have turned off the Connection blocking.

 

Could you please advise how I go about fixing this problem please?