Firefox - Rediscover the web
This was very annoying. Firefox wasn't autoscrolling with my Intellimouse 5.2 drivers. I love autoscrolling. I had used the IM 5.2 driver application-specific configuration to set the middle button click to autoscroll. Still didn't work.
Turns out there's an option in Firefox to enable autoscroll. In my install it was unchecked! Also one for "smooth scrolling" which I think is a smarter form of scrolling (w/ acceleration).
I don't recall disabling those, I wonder if some extension turned 'em off.
Worth noting if your autoscroll isn't working as expected.