From Christian Ruzicka, "with the current touch implementation on iOS the touches are not forwarded to parent views because the base implementation is not called. Also see the "Best Practices" in the iOS documentation for event handling:

http://developer.apple.com/library/ios/#documentation/EventHandling/Conceptual/EventHandlingiPhoneOS/multitouch_background/multitouch_background.html

"If you handle events in a subclass of any other UIKit responder class:
- You do not have to implement all of the event handling methods.
- In the methods you do implement, be sure to call the superclass implementation. For example, [super touchesBegan:touches withEvent:event]."

I added the missing lines and tested it with OSG 3.1.9 and iOS SDK 6.1."