I have a '94 pickup. Recently had brakes/rotors/pads replaced. Today, I wanted to lock wheel hubs to lubricate axle, but I can't turn one of the hubs to lock it. It turns very slightly, but sounds like it is hitting something. Could the brake job have affected the hub?

Yes, it's possible. The rotor is attached to the wheel hub, and you have to remove the locking hub to get the wheel hub/rotor off.