bug#3386: 23.0.94; With long lines next-line sometimes loses the column

--text follows this line--

Please write in English if possible, because the Emacs maintainers
usually do not have translators to read other languages for them.

Your bug report will be posted to the [email protected] mailing
list.

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

If lines are longer than the window, emacs forgets sometimes which is
the correct column. To trigger this bug do the following:

Create a file, say 'tmp.lst', with the following content:
 Lines 1, 2 and 4: 200 dots, '.'
 Line 3: empty
Start Emacs: 'emacs -Q'
Open the file 'tmp.lst'
"M-x set-variable" "truncate-lines" "t"
C-e
3 times 'next-line'
you end up in the middle of the fourth line instead of at its end



If Emacs crashed, and you have the Emacs process in the gdb debugger,
please include the output from the following gdb commands:
    `bt full' and `xbacktrace'.
If you would like to further debug the crash, please read the file
d:/bin/emacs/etc/DEBUG for instructions.


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)'

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: DEU
  value of $XMODIFIERS: nil
  locale-coding-system: cp1252
  default-enable-multibyte-characters: t

Major mode: Conf[Space]

Minor modes in effect:
  tooltip-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-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-x C-f t m p . l s t <return> M-x s e t - v a r <tab> 
<return> t r u n c a t e - l i n e s <return> t <return> 
C-e <down> <down> <down> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <menu-bar> <help-menu> <se
nd-emacs-bug-report>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.