Nested Web User Controls - Events Not Firing

I'm building a web user control that contains several levels of nested web user controls. The lowest child control has a button for which the click event is not being fired. 
For instance, usercontrol1 contains usercontrol2, which contains usercontrol3. usercontrol3 has button1 that, when clicked, its click event is not being fired. The load event for usercontrol3 does fire, however. If I drop usercontrol3 on a page by itself (not nested within another control), the button1 click event is fired successfully.
 What do I need to do to ensure that button1's click event is fired? I can post code if necessary, but it is quite a large amount and I am hoping that the simplified example will do the trick. Thanks in advance.
-Matt
 
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