I recently started using firefox again after trying out Epiphany for awhile. Upon returning to Firefox I was frustrated to learn that when i used my Thinkpad T23's trackpoint+middle mouse to scroll up and down as I had it previously configured it was now also causing the brower to jump to the next or previous web page depending on which way I scrolled. After some searching and was finally able to fix the behavior. I still haven't determined what caused this to start happening. I found the fix here.

Here is the fix
Vertical Scrolling seems to work out of the box in firefox if you followed the steps above. Anyway, there is a problem when you don't scroll exactly vertical, because horizontal scrolling turns into browser BACK/FORWARD commands. You can avoid this by typing about:config + ENTER in the address bar of firefox. You have to adjust the following options:

mousewheel.horizscroll.withcontrolkey.action = 3;
mousewheel.horizscroll.withcontrolkey.numlines = 1;
mousewheel.horizscroll.withcontrolkey.sysnumlines = true;

mousewheel.horizscroll.withnokey.action = 0;
mousewheel.horizscroll.withnokey.numlines = 1;
mousewheel.horizscroll.withnokey.sysnumlines = true;

mousewheel.horizscroll.withshiftkey.action = 1;
mousewheel.horizscroll.withshiftkey.numlines = 1;
mousewheel.horizscroll.withshiftkey.sysnumlines = true;
Hope this helps