As every serious organization ;-) , we use a sourcecontrol system for our projects (we as a Microsoft Partner use TFS (2010)). Unfortunately, a clientmachine of a colleague broke and he had an item in TFS locked (and was obviously not able to check in and remove the lock). This article gives in principle the answer how to unlock the item. A missing hint was to specify the workspace followed by semicolon and user (including preceeding domain and backslash).
Unfortunately, the lock could still not be removed. The TFS client stated, that the requested file is not present in my (!) workspace (something like: TF14090: Cannot unlock $/ORBIS…..list.js. It is not currently locked in your workspace.) .
This information was wrong: I had to do a TF undo operation on that item in that workspace and afterwards, everything was fine again.