1. Open the table exclusively. 2. Go into the Table Designer (for example, by typing MODIFY STRUCTURE). 3. Make a non-destructive change to the table structure. For example, you could increase the length of a character field by 1. 4. Pack the table. 5. Re-open the table, go back to the Table Designer, and undo the change you made in step 3. I can’t guarantee that this will always work, but it has saved the day for me more than once.