[airnate]

You have not stated explicitly what you want the motor to do when neither of the joystick buttons have been depressed. I assume that you want the motor to stop. This may also be the problem with the code.

i.e.
Have you programmed the motor speed to be zero when neither of the buttons are pressed?

Incidentally, the Motor Control Set Speed.vi uses an input range from [-1, 1]. If you want a range from [0-255], then you use the Set Value.vi in the WPI Robotics Library->IO->PWM->Set Value.vi You can right click on the VI and select Help for additional details about each VI.

-Nate