See if this sheds any light on it:
http://www.raspberrypi.org/forums/viewtopic.php?f=78&t=83317
specifically this:
Open /etc/modules :
sudo nano /etc/modules
And add the line you use to load the driver :
For single controller:
mk_arcade_joystick_rpi map=1
For dual controllers:
mk_arcade_joystick_rpi map=1,2
