I have not investigated the reason but I have also noticed the effect. I use the tpu-edt mappings in emacs. (It meant I had one less 
thing to learn when moving from VMS to Linux). I have to issue xmodmap ~/.Xmodmap by hand every time I log in on SL 4.4 ( i use kde).

      Alex

FRANCHISSEUR Robert wrote:
> ----- Original message from Ken Teh on Wed Mar 28 20:48:36 2007 -----
>> Many years ago, I put together a configuration which allowed many of my 
>> users to use the Jed editor in EDT emulation mode.  The configuration 
>> consisted of a VT100 translation table for the xterm application that 
>> made use the of PC keypad as an almost 1-1 map of the VT100 keypad. 
>> (The PC keypad has a single large + key while the VT100 keypad has 2 
>> keys at this coordinate).
>>
>> The trick to this configuration was remapping the NumLock key with 
>> xmodmap.  I used xmodmap to translate NumLock to an unused X keycode, in 
>> particular, KP_Equal.  The xterm VT100 translation table then mapped 
>> KP_Equal to the Gold Key.
>>
>> I'm unable to do this with SL4x.  Xmodmap's at X session startup are 
>> ignored.  Apparently, one needs to use the newer XKeyboard mechanism to 
>> remap keys.  I can remap it interactively after I'm logged in.  I took a 
>> stab at understanding XKeyboard, but it is poorly documented, at least, 
>> from a simple users' perspective.
>>
>> I am hoping someone on this list has some suggestions.  I suggested 
>> folks quit using Jed, but that didn't get me anywhere. ;)
>>
> 
>        Hello,
> 
>        I use IceWM and I can use xmodmap in my ~/.icewm/startup file
> 
>        ...
>        if [ -f .xmodmap-`hostname -s` ]
>        then
>          xmodmap .xmodmap-`hostname -s`
>        if [ -f .xset-`hostname -s` ]
>        ...
> 
>        ~/.xmodmap-rabeson          # for my Dell laptop
> 
>        remove Control = Control_R
>        remove Mod2    = Num_Lock
>        
>        keycode 0x4D =  Num_Lock        Num_Lock
>        keycode 0x6C =  Shift_R
>        keycode 0x75 =  Multi_key
>        keycode 0x6D =  Meta_R
>        ! la petite touche i sur laptop Dell
>        keycode 0x81 = F25
>        
>        add    Shift   = Shift_R
>        add    Mod2    = Meta_R
>        remove Mod2    = Alt_R
>        add    Mod3    = F25
>        add    Mod5    = Alt_R
>        
> 


-- 
  Alex Finch, Research Fellow, Physics Department, Lancaster University.
+44 (0) 1524 593618   http://www.lancs.ac.uk/depts/physics/staff/ajf.htm