Full references prevented destruction of the modem object if
it was unplugged or somehow removed. To fix that using full
references on the modems would require that all usage of
MMCallbackInfo to be aware of the validity of the modem and to
ensure the callback was called whenever the modem became invalid.
That, needless to say, would suck. Since any in-progress calls
can't complete when the modem is invalid anyway, just have the
MMCallbackInfo object return a generic error when the modem goes
away and the call is still in-progress.
Dan Williams
c0253c7c29