I have no issue with my current Firefox and with Addon installed. Did you insure the mouse driver is correctly installed?

The problem is with the wheel?

You shouldn't have to move the mouse pointer all the way over the page's scroll bar to be able to scroll normally with the wheel. That said, the wheel can work differently depending on what the mouse pointer is positioned over -- for example, an interior element in the page might have its own scroll bar so it absorb the scroll action until you hit the end and Firefox sends them to the page again.