> A further datapoint: both the above as well as (setq default-frame-alist
 > '((minibuffer))) also induce a crash in GNU Emacs 23.0.60.16
 > (i686-pc-linux-gnu, GTK+ Version 2.12.9) of 2008-11-20 on escher

I attached a fairly secure and minimally invasive patch.
Could you try it?

Thanks, martin.