I kind of have a similar problem using MS Treeview and a right-click popup menu. If you right click on the treeview and get the popup menu to show, then immediately you can click on the Activex Treeview and it will expand and collapse but the popup menu will still be there. The Activex Methods will not fire so you cannot trap for it.

The only solution I've found is to move the mouse programmatically over the popup menu so it highlights the next row and back, and then when I click on the Treeview the popup dissapears. It's another bug with a funcky workaround.
(I'm still working on this problem today, but I'm looking at the following commands: _MousePos(), AMouseObj(), ISMOUSE(), MouseMove, MOUSE AT, etc)
good luck

Andres