Engine Thrust Reversal

I have FS2002, FS2004, and FSX installed, and use them all to different degrees. The engine thrust reverse has quit working on all three, and I can't find a way to get it back. Any Ideas?

I personally, have only enountered such problem whilst using a joystick.
if you ARE using a joystick, try re calibrating it, or set it back to defaults... (Depending on if youve calibrated or not.)

if you are not using a joystick, try re installing your fs. (time consuming i know) but it might help your problem.