<p>I'm working on a MS Access database.  I've made some changes to one of the modules.  I want to go out for lunch, but when I try closing the database, I get the following message:</p>

<p>"You do not have exclusive access to the database.  Your design changes cannot be saved at this time.  Do you want to close without saving your changes?"</p>

<p>I'm pretty sure nobody else on the network has the database file open, and I don't have any other Access databases open.  I'm probably missing something obvious, but would really appreciated some help!</p>

<p>Update:</p>

<p>In the end I copied all the code, closed the database without saving, re-opened it and pasted the code back in.  I was then able to save the database.  I'm not sure if this was a one off, but I'll report back if it happens again.</p>

If you close the database and are sure nobody else has it opened, check to see if there is a .ldb file (it will have the same name as your database file).  If the file is there, then there is a  good chance it is still in use.
Is it being access by a service, like a website?
You could copy the database to another sub-directory and make your changes.  If that doesn't work, I will have to look that up.  Of course there is always the database tool, "repair and compress database..."
Is the file located on a file server?  If so check to see if any users have a file handle to it.
If it still doesn't work, update your post with your new information and we'll go further.
UPDATE (9/26):
Another thing I do when having strange issues with access databases with contain vba code is decompile.  I don't know if this is documented yet, I haven't looked in years, but it's was (at least) an undocumented switch to msaccess.
From a cmd line:
change directory to where msaccess.exe is located.
Run the following command
msaccess \path to access file\databasefile.mdb /decompile
usually runs very quick then opens the database.  Open any module and compile.
Doesn't always work, but sometimes can remove strange happenings.
Did you ever trying to copy the database to another directory and making your edits?  That should of worked; you could then rename the original and copy the file back.
Anyway, I am glad you are working again.