mouse wheel has some issues...

I've got two problems from end users claiming that their mouse wheel is not working correctly. two separate people.

when i run the same code myself, it works ok, but end users having different kind of mouse or operating system or other parameters, the mouse wheel gives some wrong events...

I cannot reproduce it myself, since everything looiks ok for me, but it might be good to test sdl's mouse wheel event handling with different hardware setups.