Internet Connection Sharing via Microsoft Loopback not working

Hello,

I use internet connection sharing over my wireless NIC, from a Microsoft Loopback interface on my Windows 7 PC.  I use it to run a program called GNS3 that lets you emulate a Cisco router.  It was working well before I installed Norton Security version 22.9.4.8.  I have tried disabling the smart firewall and setting device trust for the GNS3 virtual router's MAC and IP address, but I can't get it to work.

The Microsoft loopback is like an internal network in the PC.  It has a default gateway IP of 192.168.137.1 and the GNS3 virtual router is 192.168.137.10.  Before I installed Norton, the GNS3 virtual router sent to the default gateway of 192.168.137.1 inside the PC, which then did internet connection sharing over my wireless NIC.

Is there anything else I can try to get this working?

Is there an easy way to uninstall Norton Security?

Regards,

Ian