Following the suggestions that I found in posted replies to others who have had this or similar problems, I have found the following solution:

The page where the listbox is unresponsive is #4 in the pageframe. If I click on the tab for page #8 in the pageframe, and then go back to page #4, the problem goes away.

Page #8 has a container which contains two listboxes. The position of one of those listboxes on the screen is approximately the same as the listbox on page #4 that is not working correctly.

I have included code in the Init and Deactivate methods of page #8 to set the left property of the listbox with the same approximate screen position as the problem listbox on page #4 to -1000. And, have added code in the Activate method of this page to set the left property of this listbox to 11 (its original positions). The listbox on page #4 now performs correctly. The problem has gone away.

It is interesting to note that the problem seems to relate to the two listboxes having the same screen position. There are several other listboxes on page #4 that work correctly, and the 2nd listbox on page #8 did not have to be modified to solve my problem.

I would be interested in any comments that might explain this behavior.

Thanks,
Jim

>I have a strange bug that I can't figure out.
>
>In my form, I have a set of tabbed pages. On one of the pages I have several listboxes. Almost all of the listboxes trigger the InteractiveChange event when I select an item from their lists. But one listbox does not. I have set a breakpoint on the InteractiveChange method, and it doesn't get hit when I click on an item on the list. The listbox enable property is set to .T.
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>The odd thing: If I click on a tab of one other page in the set, and then return to the page that has the problem listbox, the listbox begins working, and will continue to work as long as that form is running.
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>Clicking on that other page alone is the only thing that I have found that causes the problem listbox to work. Clicking on no other tabs, or other controls makes the problem listbox begin working.
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>So, what is it about the other page that fixes the listbox? I don't know. I have tried putting RETURN statements in the Activate and Init methods of that page, but it still fixes the problem listbox.
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>I would appreciate any suggestions on how to debug this problem.
>
>Thanks,
>Jim