Strange behaveur for M-x

[Anakreon Mendis <anakreonmejdi@yahoo.gr>]

Hello all.
This shouldn't be a bug but I can't find a workaround for this strange behaver.
If I press M-x, instead of the minibuffer taking focus, emacs produces a beep.
I can't invoke any command except for those which a key binding exists.
The key bindings which like M-a, M-e produce a beep also.

uname -a:
Linux anakreon 2.4.27-2-386 #1 Thu Jan 20 10:55:08 JST 2005 i686 GNU/Linux

This is a "Debian testing" distribution.
Emacs version: GNU Emacs 21.4.1

If emacs is used outside the X environment, M-x works fine.

A guess is that M-x is never sent to emacs but the xev program produces
the output bellow for M-x

KeyPress event, serial 28, synthetic NO, window 0x800001,
     root 0x3a, subw 0x0, time 6331689, (166,-16), root:(172,11),
     state 0x0, keycode 64 (keysym 0xffe9, Alt_L), same_screen YES,
     XLookupString gives 0 bytes:  ""

KeyPress event, serial 28, synthetic NO, window 0x800001,
     root 0x3a, subw 0x0, time 6333198, (166,-16), root:(172,11),
     state 0x8, keycode 53 (keysym 0x78, x), same_screen YES,
     XLookupString gives 1 bytes:  "x"

KeyRelease event, serial 28, synthetic NO, window 0x800001,
     root 0x3a, subw 0x0, time 6333336, (166,-16), root:(172,11),
     state 0x8, keycode 53 (keysym 0x78, x), same_screen YES,
     XLookupString gives 1 bytes:  "x"

Any idea what's going on?

Anakreon