Very Computer

I have a very weird problem under X with my keyboard (slack 9). Xmodmap
does not work properly. My .Xmodmap is:

keycode  17 = 8 parenleft braceleft
keycode  18 = 9 parenright braceright
keycode  19 = 0 equal asciitilde
keycode  94 = less greater

naturally in XF86Config it's all set:

     Option     "XkbModel"      "pc104"
     Option     "XkbLayout"     "it"

But using alt+8 or *any* other alt-modified key, I have no output at
all. It seems like xmodmap just turned the alt-modified keys off. Let me
explain better.

It does not work if I have ~/.Xmodmap set.

It does not work if I do not have ~/.Xmodmap and on a console:

$ xmodmap -e "keycode 17 = 8 parenleft braceleft"

In every case the key by itself works properly, the shift-modified key
works.

The alt+key does not.

If anyone have noticed something like this, please tell me. Or, if
anyone knows, redirect me to some docs I can read. I haven't found
anything on google, faqs, man pages...

Here's the xmodmap output:

sensei:~$ xmodmap -verbose -e "keycode  34 = egrave eacute braceleft"
! 0:  keycode  34 = egrave eacute braceleft
         keycode 0x22 = egrave eacute braceleft
!
! executing work queue
!
         keycode 0x22 = egrave eacute braceleft

But alt+ does not show anything.

Any hints? In 5 years it never happened something like this...