Bob,
I read your message and subsequent reply. What you are experiencing is VFP's problem with handling ActiveX controls. The first item is that you are popping up a modal form over the treeview control. This does not work in VFP. You need to make sure that all forms you pop up over the control are non-modal

The second item is the GPF's you are getting. ActiveX controls are actually complete applications running within FoxPro's (or VB, Delphi's, etc) UI. These controls have their own event loops and respond to windows events. What is probably happening is that an event is firing on the object when you call another form. I had this happen to me. Whenever I would bring up a non-modal form VFP would GPF for me. It turns out that the expand event of the tree view was firing for no reason and tripping up VFP. I added code to do nothing when a flag on my form was set. Something like:

If Not Thisform.lAdding
* Do something here....
Endif

Hope this give you some insight.

Rod