I have a 3D optical mouse - Vaio. Mouse wheel works counter-wise for about 5% of times . That occurs more often as the speed of my scrolling increases. Do you think the problem is hardware-related ? Because I bought it recently and it doesn't have any sort of warranty. If not , how could it be solved?
Depending on the kind of method used to detect the movement of the wheel, it can be just a piece of hair or a bit of grease obstructing it or maybe it can be also a defective sensor. Try to open the mouse and clean the wheel sensor gently with a soft brush.
This tutorial may be of help: The illustrated guide to Wacom mouse scroll wheel adjustment and cleaning. It's for a different mouse model, but today all of them are more or less the same ;-)