A lot of times, TFS acts flaky and the best thing to do is to clear the local cache.
DELETE THE CONTENTS OF:
C:\Users\[User]\AppData\Local\Microsoft\Team Foundation\5.0\Cache
Rename Computer Name in Case TFS Gives you Workspace Problems
When you are setting up TFS through Visual Studio, and are trying to map a drive, TFS may give you an error saying that you can’t and that profile exists on the TFS server. It may be because the account+computername+workspace (they’re all bound) is already on the server.
The way around this is to rename the machine. This may have happened because the virtual machine was copied.
Be aware: IF YOU DO THIS, other programs that have the computer name saved to it under privileges, like SQL Server, may have to be changed. In SQL Server, you may have to login via the sa account or through single-user mode.