I just ran into the same issue. I created a startup script that modifies the keymap.xml, so I can update my miraclebox premium again without issues It just replaced the "InfobarActions" section of the keymap.xml with the additional entries needed for the miraclebox remote control...
For creating the startup script, place the attached file 'user.txt' in /etc/init.d, remove the .txt extention, make it executable (chmod 777 user) and link it from /etc/rcS.d (ln -s ../init.d/user S80user).