I have a file that I have been working on in sketchup. Now Every time I open it it an error box pops up and says "this file is locked by another user. Do you wish to open the file as read only? Yes/No" If I select no, it does not open the file. If I select Yes, it will not save the file. (I can click Save As and rename it) As far as I know, I'm the only user on this machine... What the FOO?