Do you have a pdf open in another tab? I found that if I had a .pdf file open the scrolling would work in the .pdf, but not in any of the other tabs. Closing the .pdf allowed for scrolling again.

No, I do not have a pdf open in any other tab. I closed all other tabs except one and even then it does not work. I am finding it quite inconvenient and irritating to scroll using scroll-bar everytime as I am used to scroll withtrackpad.

Is there any way to roll-back my firefox to earlier version without uninstalling?

Steve85 - you are correct. I found that too. But what an inconvenience. It never happened in 3.5. There must be some reason for this and a fix.

yes, this is a bug and firefox should fix it asap..