I too had this problem, but after installing/reinstalling trackpoint drivers on my thinkpad it works. Doesn't really make sense because scrolling was fine in every other program but firefox 4.

In my case this problem is related to the Adobe Acrobat Reade plug-in. Whenever I open a PDF file using the plug-in, the scroll stops working.

Everything goes back to normal when I close the tab with the PDF file.

Hi!

Without information about the hardware used it is hard to make an accurate guess but the below post MIGHT work if you have an ALPS pad:

https://support.mozilla.com/en-US/questions/791829#answer-163071

If not then you will not find the file at the specified location. You might however find here:

C:\Program Files\Synaptics\SynTP\TP4table.dat

or

C:\Windows\system32\tp4table.dat

If so then please try to apply the same fix (you can just undo it should it not work!).

Good luck!