I installed this on my 1.5.5a and the installation went fine (except I had to do manual install - plugin manager doesn't exist)
Admin area came up with something like "Ultimate URLs installed successfully" in a green box :)

I can see and enter the setup for the module and it's showing as Enable alternate URLs? = true but my urls are still showing as :
http://www.skysports.com.au/index.ph...roducts_id=281

Do I have to do something to kick off the process?