Problems with mousewheel

Okey, here is the problem, when I scroll my mousewheel down (mwheeldown) like 1/3 or 2/3 times it goes mousewheelup for no reason. It really sucks, because I have mwheelup +duck and mwheeldown +jump. So I'm just jumping a map, scrolling down, it does doubleduck insteed of jump and i'm like wtf? fall... But I need mwheelup +duck, cuz with it I can make my runs faster. Here is a video how I tried to scroll down the page... (I used only mwheeldown in the video)

http://www.sendspace.com/file/n7bzp5 388KB

I already posted something about this. http://xtreme-jumps.eu/e107_plugins/forum/forum_viewtopic.php?71272.0#post_75107