KB2750149 causes problems on HTTPS connections behind TMG proxy/firewall

I’ve been experiencing a lot of troubles authenticating to Team Foundation Server of my company for five months, and today I’ve finally got the cause of them and the solution.
Our TFS is installed on a Windows Server 2012 and published over HTTPS and we can get it through a TMG 2010 proxy/firewall.

Some months ago we migrated our old TFS 2010 to the new version and at the same time, some clients from Windows 7 to Windows 8: it was when we started having those problems!
If we tried to connect to it using Visual Studio 2012 we received the strange error: “TF30063: You are not authorized to access [project]”.
What’s this?!? I was using the TFS admin credentials!

I fought against it for a long time trying a lot of solution from the web but none of them solved the issue:

  • Someone suggests to clear the IE cache.
  • Someone suggests to modify settings on IIS
  • Someone suggests to install TMG client
  • Someone suggests to clear credentials saved in Credential Manager
  • Someone suggests to add TFS website to Intranet zone on IE
  • I’ve installed and uninstalled several times Team Explorer 2012 and 2010

None of them fixed the problem. Anyway last week I got the right way and today I’ve finally solved it: the issue is related to the KB2750149. This update has some known issue with the Failover Cluster Server fixed by the KB2803748…and now we’ve found another one!

After having uninstalled this update and restarted my pc I was able to connect to TFS again. Unfortunately this is a very important update solving several issues about .NET framework 4.5, so be very careful before uninstalling it!