[plt-scheme] Dialog% not accepting frame% subclasses as parent?

It seems to work for me:

(define f (instantiate frame% ()
            (label "frame")))
(define d (instantiate dialog% ()
            (parent f)
            (label "")))
(send f show #t)

what version of DrScheme are you using?

As far as sheets go, I'm not an expert, but I think that the only way
is to create a parented dialog (as above).

Hth,
Robby