>Questions...
>1. Under what circumstances can _screen.activeform not be of type 'O'?

When there is no active form? It can happen.

>2. Can _screen.ActiveForm.BaseClass be anything other than 'FORM'?

When it's a toolbar? Though they don't take focus, so I wouldn't expect it to be activeform - I've been caught out before when it doesn't do what I expect!