the tolerances between the hub and the wheel are very close on some cars. like the other poster said kick or somehow pry the wheel from the hub. just make sure you put something under the car so it doesnt fall on you.
It's corrosion! Screw 2 of the studs back in a few turns. Take a sledge and beat the tire wall a couple of times from the front and the back. It will come off. Be careful not to hit the rim they are not real happy about being beat on with a sledge. The idea to spray some WD40 on the wheel where the rim contacts the hub often helps as well. Let it sit for a few minutes and then whack it with the sledge. Amateur Tip !!! don't be afraid to hit the thing! But be careful, sledge hammers have a nasty little way of hitting back sometimes when they contact rubber. And for god's sake, make sure you screw a couple of the studs or lug nuts back on a couple of turns! Good luck!