[ESS] sometimes <C-x s> does not work ...

[Meinhard Ploner]

I have a very strange problem. I work with R 2.3.1 on Mac OS X 10.4  
and use ESS 5.3.1.

I save my files using C-x C-s, which usually works fine, but  
sometimes it does occur that the command works only if I put the  
shift for the second command, looking now like C-x C-S or C-x C-shift- 
s, which is awful for me.

Restarting emacs, ess and R resolves the problem, BUT: why this does  
occur to me??

Meinhard Ploner