Maybe one of these from Debra Dalgleish's site will help:
http://contextures.com/xlfaqApp.html#ReadOnly
http://contextures.com/xlfaqApp.html#AlreadyOpen

Jim Murray wrote:

Why am I getting a "Locked for Editing" error on a non-protected file? When
I open the spreadsheet on a fresh boot, no problem. If I close and try to
re-open the file, I get the "locked for editing" error message. It is not
protected. It also says the file is already running. But, I cannot find it
anywhere. When I reboot, the file opens normally, until I close and try to
re-open it. As a safety measure, I saved the file to two more computers and
they are doing the same thing. All three computers are running XP Pro and
Office 2003. I have been using this file for about ten years and have never
had this problem before. For some reason, when I close the file, it is not
shutting down completely. Any help will be appreciated, Thanks you, Jim
--
Jim

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Dave Peterson