I saw this advice on another website, maybe it will help you.
It would appear that other people are having the same problem.
Here is the MSDN documentation
Upon installing Visual Studio 2012, I found out that all operations related to TFS (such as adding a new file, check in/out, etc.) were incredibly slow and would freeze the application for quite some time. If this is the case for you, try this solution:
Edit the Visual Studio config file found in C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE\devenv.exe.config
and locate the following line:
<system.net>
Right below (above settings, NOT under), insert the following line of code:
<defaultProxy enabled="false" />
Your visual studio should now be more responsive!