It sounds as if you're using the form to a record, and you're trying to clear all the fields to let them start over.
Once the user begins entering data into the "new" record, an actual record is created. The record is in a pending state while they're entering the data. You can see this in the icon on the record selector bar - it changes to a pencil whenever the pending state is in effect.
If you save the record, the pending state is cleared. It is also cleared if you press Escape, or call the form's Undo method. But if you just change fields to Null, the pending state persists. Again, you can see this by looking at the record selector bar.
I believe you're getting the error because whatever operation it is you're trying to do isn't allowed when a record update is pending. Instead of setting all the fields to Null, you probably need to call Me.Undo to clear the pending state.
Rick Sprague
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