[AUCTeX] time stamp not being updated properly?

[Rajarshi Guha]

Hi, when I start a new LaTeX document my file gets a header like:

%%
%% ws.tex
%% 
%% Made by Rajarshi Guha
%% Login   <address@hidden>
%% 
%% Started on  Tue Jul 11 10:41:33 2006 Rajarshi Guha
%% Last update Tue Jul 11 10:52:15 2006 Rajarshi Guha
%%

However when I do a C-x C-s to save the file the 'Last update' line 
does not update properly - it drops the initial comment characters, 
so doing a save gives me

%%
%% ws.tex
%% 
%% Made by Rajarshi Guha
%% Login   <address@hidden>
%% 
%% Started on  Tue Jul 11 10:41:33 2006 Rajarshi Guha
Last update Tue Jul 11 10:55:12 2006 Rajarshi Guha
%%

Does anyone know how I can fix this? I'm running Emacs 21.4.1, 
Auctex 11.55.3 on
Ubuntu Dapper.

Thanks,
Rajarshi