If you're using anything other than a dial-up modem, it shouldn't affect your dwnld speed. I've never heard of cable/broadband where the 2 are related. You'll normally have a separate max upld speed & a max dwnld speed provided by your isp. So they shouldn't affect each other.
Whenever you change the upld setting within LW, you need to press the 'Apply' button! Don't forget. The only other option I can think of is that you change your setting to a lower type of connection. This will affect the way the controls work.