front end problem-caliper seized, bad wheel bearing?

2003 grand caravan 3.8L. wife came home with left front wheel smoking. smelled like brakes to me and rotor was extremely hot compared to other side. jacked it up and wheel was barely turnable by hand while right side was fine. took wheel off. the center of rotor seem much hotter than disc. just since disc of rotor dissapates the heat better than the center? or problem with wheel bearing? I assummed the caliper frozen. once everything cooled down I could turn wheel by hand easily. I replaced the caliper. took test ride and everything fine. wife gone today and said bad noise coming from front. goes away when hit brakes. thumping kind of noise when start off and gets faster as you go faster. I verified it. went to loosen lug nuts and found ALL of them loose? I tighten them pretty snug just two days ago. have never haven a lug loosen before. I tighten them all up and went for ride and seems fine. so think these loosened lug nuts are caused by something else? could a bad bearing cause nuts to loosen up and also cause the caliper to lock up since maybe caused uneven pressure if wheel is rocking? could the wheel studs have loosened up in the hub when hub was real hot so that even though the nuts were tight, the studs could move and loosen everthing up? or think it was just bad caliper and I just didn't tighten up lug nuts enough?