X-Window and AfterStep

[homega@vlc.servicom.es]

After adding new applications (eg. /opt/netscape/netscape), to
/etc/X11/afterstep/menudefs.hook, the menu works fine for a while, but after
some time, menudefs.hook goes back to its original configuration, wiping out
any trace of the new additions (well, it keeps them on menudefs.hook~). 
What's the reason for such behaviour?

Also, I can run `startx' as a normal user, and even as root, though I can't
run it if I'm logged in as SU, is this normal?
homega:~# startx
bash: startx: command not found

TIA,

Horacio.