[Alan Anderson]

I am guessing your code is doing something like this:

if button 1 pressed
  then run motor forward
  else stop motor
endif

if button 2 pressed
  then run motor backward
  else stop motor
endif

Button 2 will work. However, if you press button 1 the motor will run but will immediately be stopped by the button 2 code.

Instead, try this:

if button 1 pressed
  then run motor forward
endif

if button 2 pressed
  then run motor backward
endif

if neither button pressed
  then stop motor
endif

You might also want to explicitly deal with both buttons pressed at the same time.