Ng ( or Kit? Forgive me if I'm rude--it's unintentional)

Then you must have a grid on your form. I've often in the past had grids go bad, but not like this. Again, I don't have any *real* advice, except I would be interested in whether it still chokes on a subset of the data. Could you do a test with only a few hundred records?

HTH

>I have a parent table and a child tables with around 30000 records each. I
>created a input form and added those tables in DataEnvironment. I created a
>one-to-many relation for them as well. I drag a key field from the parent
>table and whole child table from DataEnvironment to my form. Then I run my
>form. It seems work fine. But when I run it again after print any report in
>preview. My form display a error like this:
>
>This program has performed an illegal operation and will be shut down.
>If the problem persists, contact the program vendor
>
>For test purpose, I create another set data and generate 30000 records
>manually for both parent and child tables in another PC. And create a new
>form, add the tables and build the relation in DataEnvironment. Drag the
>key field from parent table and whole child table from DataEnvironment.
>Then run a report in preview mode and my testing form. I got the same
>result! Anybody help me!