On a form with 2 child files linked to the master file [ the master file has no data changed ], the error "this key value is already in use" appears when moving off the the current child files to select the next master record. Both child files have data entered for each master file record. Where most likely does this occur and what can cause it? What can prevent this situtaion? This is paradox 8 running on an NT server.
Any help will be appreciated. thanks,

The child tables use keys?

Do they have a composite key (2 or more fields) or a single key?

Can you describe in detail the relationship between the three tables?