Firefox comes included in the shiny new Ubuntu, has slightly different fonts (need to get used to that) and changes behaviour of mouse buttons. So you need that one to get FF to behave, and you need this link to get the buttons to work if they don’t.
Just so you know,
Hugo.
PS: That’s the second thing I spotted. First thing I spotted: be careful with your grub menu, do not go for the “3-way merge”. No biggies there, but resulting entries are funny (all ubuntu 8.04) :)