C-M-a not working, describe-key doens't help, how to debug

[muthu kumar]

Hi All,
         I'm having a strange issue. I'm fairly new to emacs and I recently found out that
         C-M-a takes you to the beginning of function. but C-M-a on my Kubuntu 7.04 installation
         doesn't work. 
          I tried debugging it with describe-key, pressed C-M-a and it acts as if I didn't press anything,
          so just to make sure I pressed C-M-z and it said correctly that "C-M-z is undefined".
 
         How do I debug this issue  ?

         My emacs version is 21.4.1 of 2007-08-28 on terranova, modified by debian ( version inside emacs ).

Thanks & Regards,
Muthu