You're right, my mistake.  I'm getting confused with all the tests I've been running.

 

I have found the cause behind my problem.  To recap, the open dialog does not appear with Flash enabled and Silverlight disabled.  I've found that if I remove the ValidateOption tag (see markup in my first post) that specifies the file types allowed (AllowedFileExtensions), the dialog will appear.  I'm searching for another way to specify this (either in code or declarative markup).

 

This must be unintended behavior, please investigate.

 

Thanks,
David