Before I start ripping into this did something change since 1.60 that may cause this?
No. This has nothing to do with the BrowseDialog class, but rather the .NET serialziation designer. In fact, we take this same approach for all of our browse dialogs in our medical app (and I even created a new one this morning). One thing that helps, though, is to set the class structure up like a form or user control with the designer file: