does your mouse have a wheel ? If so, it might come from it.
If you have a laptop with a pad, then try to update its drivers.
In both cases, you can also open your "Tennis.ini" and change this line, under [Menu], from :
WheelAxeMode = -1
WheelAxeMode = 0
so the Wheel will be totally ignored.
== Mana Games ==
>> I don't answer Private Message, except if it's really a _Private_ topic <<