QARun Ver 4.7.4
Win XP Home

When driving the AUT manually, the button functions as expected (adds the selected item to a list).
However, when driven from QARun, the item does not add to the list.
I have verified that the button is, indeed, pushing in by using a pause between a Left Down and a Left Up.
I spoke with the developer who wrote that UI and code, who verified that the button was a standard class but that the message sent by the button was a custom message.
Any ideas?