bug#3579: 23.0.94; Customize: Cannot see error messages if use standalone minibuffer

Can't give a great recipe for this - you have to set up Emacs to use a
standalone minibuffer (separate frame) only. That's all you need to
do, I believe, to reproduce it.
 
Edit an option value to make it invalid - e.g. edit an integer field
to be 2.5. Then choose Set for Current Session in the State menu.  You
will not see an error message in the minibuffer frame (which is where
the echo area is), or anywhere else. The message does get logged to
*Messages*, but the user gets no feedback at all.
 
Note that mouseover messages appear fine in the echo area.  E.g. turn
off tooltip-mode and put the mouse over the State button. You will see
the text in the echo area. Likewise, other Emacs messages, as produced
by `message' and `error', for instance, appear fine in the echo
area. It is only Customize messages that do not appear anywhere.
 
 
 
In GNU Emacs 23.0.94.1 (i386-mingw-nt5.1.2600)
 of 2009-05-24 on SOFT-MJASON
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4)'