Diagnosis
You tried to assign a field a short name that cannot be used in thisform. This can have three reasons:
1. The short name was already used for another field.
2. The short name is a reserved word.
3. The field already had a short name and is being used. The new shortname is longer and means that the existing space for notation of theusage is exceeded at the places where it is used.
Note that this error can occur if you try to swap the short names oftwo fields in a dialog step.

Procedure
Choose a different short name for the field.