someone might help but i guess you must first post more details. ex. your current xorg.conf (at least the InputDevice section), the type of mouse you're using, mouse brand, perhaps modules too (lsmod output) or anything more?
you might as well check this howto from gentoo. just in case you haven't seen this yet.
http://gentoo-wiki.com/HOWTO_Mouse_Scrollwheel
here's an article for logitech too:
http://www.linuxnetmag.com/en/issue5/m5mouse1.html
darn this. there's nothing more i can do this time than refer people to howtos. oh well at least i can help. not a bad idea anyway.
regards
Edit: here's a solved topic:
http://www.linuxquestions.org/questi...d.php?t=111394