backup-directory-alist not always honoured

[Chris Moore]

Very occasionally I see my backup files are created in the wrong
place, but I've been unable to reproduce this behaviour.

I have this setting:

  backup-directory-alist is a variable defined in `files.el'.
  Its value is (("." . "Backup"))

The idea is that backup files are created in a subdirectory of the
directory containing the file itself, called "Backup".  This works
99.9% of the time.

However, I recently found this backup file:

  
./cur/1165087471.P20227Q7.chrislap:2,S/1164450633.P2139Q0M622761.chrislap:2,S.~1~

It is a backup of this file:

  ./cur/1164450633.P2139Q0M622761.chrislap:2,S

For some reason it was created in:
  ./cur/1165087471.P20227Q7.chrislap:2,S/
instead of in
  ./cur/Backup/
as I would expect.

Looking in ./cur, I see 2 subdirectories containing backup files:
  ./cur/Backup:2,S/
and 
  ./cur/1165087471.P20227Q7.chrislap:2,S/

but no "./cur/Backup/ directory at all.  I don't know if there's
anything special about files with ':' or ',' in their name which might
be confusing Emacs.






In GNU Emacs 22.0.91.19 (i686-pc-linux-gnu, GTK+ Version 2.8.20)
 of 2006-12-03 on chrislap
X server distributor `The X.Org Foundation', version 11.0.70101000
configured using `configure '--with-gtk' '--with-xpm' '--with-jpeg' 
'--with-png' '--with-gif''

Important settings:
  value of $LC_ALL: en_GB.UTF-8
  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
  locale-coding-system: utf-8
  default-enable-multibyte-characters: t

Major mode: J-Shell

Minor modes in effect:
  show-paren-mode: t
  display-time-mode: t
  iswitchb-mode: t
  dynamic-completion-mode: t
  shell-dirtrack-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
T h e SPC f u n c t i o n s SPC w h i c h SPC a l l 
o w SPC y o u SPC t o SPC v i e w SPC r e c e n t SPC 
k e y s t r o k e s SPC h a v e SPC b e e n C-j h i 
d d e n SPC b y SPC j - s h e l l , SPC t o SPC p r 
o t e c t SPC p a s s w o r d s SPC e n t e r e d SPC 
i n SPC s h e l l SPC b u f f e r s .