JonH:
I am assuming that this is a secured database
Are you getting the error when you try to enter the database or when you try to repair it. That is to say, does someone alert you to the fact that there is a problem and when you try to enter you get a message stating that there is a problem or are you just trying to compact / repair the database on a regular schedule and are getting the error?
Most of the time what you will find is that someone is not shutting the database down properly, i.e. they are turning off their computer with it open. Use notepad to view the contents of the ldb file to see who was in the system when it locked up. Do a reboot on their machine to see if that will release the ldb.
If you have Tools - Options - General - Compact On Close turned on in a multiuser environment this can also cause problems. Turn it off.
Make sure you are using Tools - Options - Advanced - Edited Recordlocking.
I have also found that if I exit my database and try to reenter it immediately (like 1-2 seconds later) that it will not have enough time to release the ldb and will lock up.
Solution is to delete the ldb file. Several methods might have to be tried to accomplish this. First is a straight delete. Second is a rename and delete. Third open the security.mdw file just like you would a database, preform a repair if necessary and exit. Forth is reboot the server.
Good Luck,
Autoeng