Problem adding ItemAdded event handler (IActiveViewEvents)

This is driving me batty. I have an add-in that works fine on 10.1 but not 10.0. With some judiciously placed breakpoints and exception catchers, I can see that the problem has to do with adding an ItemAdded event handler. Please see the attached exception message (sorry about the redacted file names).

Does anyone have a clue how to make this work?

Thanks,
Evan.

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