When things go wrong - This batch is being posted by another user

You get this message even though nobody is logged in to the database so that it's impossible for the batch to be being posted by somebody else. What to do?

1.  Back up the DYNAMICS and company databases.
2. Change the batch status so that it no longer thinks it's being posted.

USE YourCompanyDatabaseName
GO

UPDATE SY00500 set BTCHSTTUS = 0 WHERE BACHNUMB = 'YourBatchNumber'