Hopefully this will help someone else…
I’ve run into issues where I get help desk cases saying that a document is locked in SharePoint and the user can’t get into it. Of course, my first thought is that someone has it checked out. But when I go out to see who has it, the answer is… no one.
The real issue ends up being an internal document lock in the file itself. Microsoft covers that in this KB:
You receive a “<FileName> is locked for editing by ‘another user’” message when you try to modify a document in Windows SharePoint Services even though you are the user who previously opened the document
This normally happens when the person’s computer crashed or locked up during a previous edit session with the document, and the file wasn’t closed properly.
When a document is opened by a client program, Windows SharePoint Services puts a write lock on the document on the server. The write lock times out after 10 minutes. Users cannot modify the document during the time when the document is locked.
In a scenario where the program that opens the document unexpectedly quits or crashes and you try to open the document again before the write lock times out, the message that you receive says that the document is locked by another user. This behavior occurs even though you are user who previously opened the document.
The solution is to wait 10 minutes and try it again.
Sometimes ignoring problems *do* make them go away…
(cross-posted from my blog at http://sharepointduffbert.com/2012/11/06/the-dreaded-is-locked-for-editing-by-error/)