I am struggling to solve a problem with Team Foundation Server (yeah, I should just go with Git, I know...). We are working on a mid-sized solution (<20 projects) and suddenly in my workspace I cannot make check-ins or check-outs anymore. Everytime I try to, I get a very generic error message:
An item with the same key has already been added.
This is either shown in a dialog box, in the output window of Team Foundation Server or at the top of the Team Explorer window in Visual Studio 2013.
I already tried deleting the TFS cache located under
C:\Users\[my username]\AppData\Local\Microsoft\Team Foundation\5.0\Cache
and
C:\Users\[my username]\AppData\Roaming\Microsoft\VisualStudio\12.0\Team Explorer
Cleaning the solution does not help, and neither does restarting Visual Studio. Other members of my team still can do check-ins and check-outs. Also I found that the issue is not only related to this solution (although it was the only one I have been working on the last few weeks). Regardless what project I try to open, I get the same error message from TFS. However, if I choose another workspace and try to open projects from there, no error appears and all just works as usual.
Any suggestions on how to resolve the issue?