Rog,
check the mapping in AH to be sure the axis is assigned properly first! if thats ok the ,the saitek control panel,if installed if not use windows game devices and check to see if the axis works there.
If you find it not working,check the wire between the throttle and joystick,they come loose and it's possible to bend a pin so as tocause problems. you can replace the wire with a ps2 wire available at most bigbox electronic stores. The X52 uses halon devices and not pots so they rarely go bad but I understand they can be dislodged from their place. I have an old X52,it's 10 years old now and still works fine,I quit using it when I bought at warthog a couple years ago.
Generally I find if you secure the wire from throttle to joystick so it cant move and use a powered usb hub you will have very few issues with the setup,some of the button might wear prematurely but for the cost it's a pretty good value.
Check the wire ends closely,I used a magnifying glass to see, and make sure all the pins are straight and all there!
hope this helps!