Hi Brett,
You should never have to use SET DATASESSION in a form's methods. It is as dangerous as they make it sound in the docs.
If you are trying to have a form share the same data session as another, then follow these steps:
1) Your parent form can create it's own private datasession or not. Just choose your desire in the data session property of the form
2) Your parent form MUST have the data session property set to "Default Datasession"
3) Write the code to launch the child form, but put it into a method of the parent form.
If you follow these steps, then the child form will use the same data session as the parent form.
Hope this helps!
-Chuck Urwiler, MCSD, MCDBA