bug#2182: 23.0.90; < fails in rmail mode

In a RMAIL file, in mbox format, typed < which used to go to first
message; instead i got

Debugger entered--Lisp error: (wrong-type-argument number-or-marker-p t)
  rmail-show-message(t)
  rmail-show-message-maybe(t)
  rmail-first-message()
  call-interactively(rmail-first-message nil nil)

reproducable every time
Mail file has 18400 messages


In GNU Emacs 23.0.90.2 (i686-pc-linux-gnu, GTK+ Version 2.12.0)
 of 2009-02-03 on cardew
Windowing system distributor `The X.Org Foundation', version 11.0.70200000
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_GB.UTF-8
  value of $XMODIFIERS: @im=local
  locale-coding-system: utf-8-unix
  default-enable-multibyte-characters: t

Major mode: Debugger

Minor modes in effect:
  auto-image-file-mode: t
  show-paren-mode: t
  display-time-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k 
C-k C-k C-k C-k C-k C-k C-k C-k C-k <down-mouse-1> 
<mouse-movement> <mouse-movement> <drag-mouse-1> <help-echo> 
<down-mouse-2> <mouse-2> <down-mouse-1> <mouse-movement> 
<mouse-1> <return> C-x i . s i <tab> <return> <escape> 
> <backspace> <backspace> <backspace> <backspace> <backspace> 
<backspace> <backspace> <backspace> <backspace> <backspace> 
<backspace> <backspace> <backspace> <backspace> C-c 
C-c x <return> o <return> C-x b <return> <backspace> 
7 C-x C-s C-x b <return> C-x o d d SPC d d d f m d 
v SPC C-c C-c <return> C-x o n d d SPC d d t f <help-echo> 
<down-mouse-1> <mouse-movement> <mouse-movement> <drag-mouse-1> 
<down-mouse-1> <mouse-movement> <mouse-movement> <drag-mouse-1> 
<help-echo> <down-mouse-2> <mouse-2> <down-mouse-1> 
<mouse-movement> <mouse-1> , C-d C-d C-d C-e C-d <down-mouse-1> 
<mouse-1> C-a C-k C-k C-e <return> C-x TAB . <backspace> 
C-x i . d i r <tab> <return> <escape> > <backspace> 
<backspace> <backspace> <backspace> <backspace> <backspace> 
<backspace> <backspace> <backspace> <backspace> <backspace> 
<backspace> <backspace> <backspace> <backspace> C-c 
C-c x <return> q <down-mouse-1> <mouse-movement> <mouse-1> 
<escape> < <down-mouse-1> <mouse-1> <down-mouse-1> 
<mouse-movement> <mouse-1> <backspace> C-c C-c x <return> 
o <return> C-o <backspace> <backspace> <backspace> 
<backspace> <backspace> <backspace> <backspace> / m 
n t / s n <tab> m <backspace> h o m <tab> j <tab> p 
<tab> F <backspace> S P <tab> F e <tab> <backspace> 
<tab> <backspace> <tab> <tab> F e b <return> y e s 
<return> C-x o t <down-mouse-1> <mouse-movement> <mouse-movement> 
<drag-mouse-1> d d SPC SPC SPC SPC SPC SPC SPC SPC 
SPC SPC SPC d d d d SPC d d d SPC SPC d SPC d SPC SPC 
SPC SPC SPC SPC SPC SPC SPC SPC SPC SPC SPC SPC SPC 
SPC SPC SPC d d s y <return> <escape> < < q < q <down-mouse-1> 
<mouse-1> < q < M-x r e p o r t <tab> <return>

Recent messages:
Saving file /home/jpff/RMAIL...
Wrote /home/jpff/RMAIL
Mark set
Entering debugger...
Back to top level.
Entering debugger...
Back to top level.
Entering debugger...
Back to top level.
Entering debugger...

==John ffitch