I talked to you on AIM... but it's good to have it posted and archived too.
First off, make sure the tabs are punched out on the big nut. Put the wheel back on, and put the car on the ground, with the E-brake on and in gear. Now use a big breaker bar/ratchet (1/2" or 3/4" if you have one), and a cheater to put all your weight on it, it will come off. I have had to do this a few times, when even the impact gun won't budge the nut. For some reason it's always worse on the driver's side...