2001 Yukon- ignition won't turn

When I put the key in the ignition of my 2001 Yukon, it will not turn at all. It has a remote starter and passlock, don't know if that would have anything to do with it. I'm thinking it might be the cylinder, but if anyone has any other ideas before I have it towed to the dealer, that'd be great. The engine starts with the remote starter, but the key still won't turn. The steering wheel isn't locked. Any ideas??

Thanks!