Exception Message: Unable to create the workspace due to a mapping conflict. You may need to manually delete an old workspace. You can get a list of workspaces on a computer with the command 'tf workspaces /computer
I got the issue by deleting a broken build on our build server and then trying to recreate the build with the same settings in visual studio 2012.
It appears that the Network Service holds on to the mappings of the orginal build under the workspace it created for this.
In order to solve this i had to delete the original workspace from the network service using the following command:
C:\Program Files (x86)\Microsoft Visual Studio 11.0>TF workspace /delete /collec
tion:http://<YOURSERVERNAME>:8080/tfs/defaultcollection <WORKSPACENAME>;"NT AUTHORITY\NETWORK SERVICE"
The workspace name is displayed in the error messgae when you attempt the new build and it fails, it will be something along the lines of 7_1_<YOURSERVERNAME>.
You can also get this information using the TF workspaces command as suggested in the exception message.