I've seen the same thing. Users, when they install an update, think that everyone is out, but they come to find that someone is still in. When they do get that person out, its still a problem. So the first update attempt fails, and it results in a filelock until a restart.

>Restarting the user machine. It seems that sometimes Windows keeps locks until the user restarts.
>
>I don't know of any other method to unlock the file.