Server 2003 looses internet

Hi,
I have a strange problem, I am not sure if anyone seen something like this. I wanted at least discuss it because it seems very strange.

I have a network with a Win2003 server as a domain controller and some 30 Windows 7 workstations. The server is mainly a file-sharing server. In addition it functions as a DHCP and DNS and the DNS uses opendns.
Today I had one workstation installed new and decided to put on windows 10 instead of windows 7.
All was fine but when I disable the network connection on this new Windows 10 computer and than enable it again, the server looses its internet connection and of course so do all the workstations including the new win10 machine.
If I reboot the server all is ok again. This said, only the internet is off but the actual local network keeps on working fine.
However, I can actually reaped this example and it happens every time.

I never had anything like this happen and I am troubleshooting and wondered if anyone heard of something like this and maybe has a pointer.

This server is running for 5 years without issues. I do not believe it is actually the server but instead that either some firewall is triggered or the DSL modem. I know it is a long-shot but anyone had anything like this happen?

Best wishes,
Thom