Just as a couple of troubleshooting questions:
1. When you put the mouse pointer over over the IAS/MACH Selector knob does it change to a pointing hand?
2. Does a Tooltip with "IAS/MACH Selector" appear?
3. With the pointer showing as a pointing hand and you roll the mouse wheel up or down, what happens (I suspect nothing as this appears to be the main source of your frustration!)?
4. If you perform the same procedure over any other knob (Alt/Hdg/Radio Tuner/etc) what happens?