I figured it out. The problem was that I needed to do a THISFORMSET.Release (within the main form) when the main form was closed. The second form was not visible when the first form was closed, and therefore that, and the formset, stayed open with no way to close it. Thanks for the advice anyway! (I think I need to increase my caffeine intake to cope with the form event model...)

>It's got to be something not being released on that second form. Maybe you could check by deleting each object on the form one at a time until the problem goes away...
>
>>This is defitely related to the second form in the set. I removed the second form and the problem went away. I then re-created the second form, copied all of its controls back from the earlier version, and the problem came back.
>>
>>I guess this is going to be one of those things I'll never figure out and will just have to work around via trial and error.