I disabled mine PHYSICALLY and PERMANENTLY after having the same problem (randomly clicking on it's own and movement in some directions didn't work).
I opened up the phone, and pulled the silver / black cover off the little joystick.
I then grabbed the joystick with a pair of needlenose pliers and litterally yanked it off the circuit board (it will come off fairly easily).
I then stuck a little piece of foam (the spongy packaging kind) in it's place to hold the silver joystick button in it's original position.
Once the phone is re-assembled, you can't even tell anything is different except that the joystick doesn't function anymore.
The only thing I found I cannot do without the joystick is zoom the camera in and out. I'm sure there must be an alternative way, but I haven't been inspired to invest any time into finding an alternative.
Here are the dissasembly instructions I followed:
http://www.bellybuttonporn.com/wiki/...ur_PPC/XV_6700