Nuget package server

I have opened a question on SO about an authentication issue:

http://serverfault.com/questions/377333/teamcity-nuget-feed-http-authentication

This is all with vs 2010, because vs 11 is not working at all, instead it produces this error:

Could not connect to the feed specified at 'URL'.  Please verify that the package source (located in the Package Manager  Settings) is valid and ensure your network connectivity.

Any help appreciated!