When you use different (virtual) machines to check out files in Microsoft TFS 2010, different workspaces are used. If you forget to check in a file on machine A, you can’t check that specific in on machine B. To solve this problem there are multiple solutions:
1. Start machine A en check the files in.
2. Use the TFS administration application if you have sufficient rights.
3. Delete the machine A workspace in the Source Control Explorer on Machine B.
After deleting the workspace I could check the files out and in again.