Getting error "Unable to join player connection multicast group." on every project load

Unity Engine
1

After opening any project i get these errors (Windows 7 x64; Unity 5.1.0.f3):
Socket: unable to join multicast group, error: The requested address is not valid in its context.
(0)
Unable to join player connection multicast group.
Socket: unable to join multicast group, error: The requested address is not valid in its context.
(0)
Unable to join player connection alternative multicast group.

I have tried refreshing the license, and creating a new licence; as well as installing Web player as suggested here:

If I start windows without network cable connected and run Unity, this does not appear. After I plug the network back in, and open any project, I get these errors again. I’m sure it has something to do with the new router that was set up by my ISP. I tried to search online, and have found nothing of use, and tried Enabling IGMP Configuration on the router, which didn’t help. Temporarily disabling the Firewall also didn’t help.

I did send the bug via Editor form. However, someone here may have some advice to share.

2

The same here, same errors on every Unity Editor start since I installed 5.3.0f4.

3

For me, this just went away by itself. Not sure what it was…

4

Me too;on Unity 5.4.0f3(64bit).