i have this same issue where the button is stuck. i am also not under warranty. i actually took apart the phone, cleaned the button, the casing. made sure no corrosion on the contacts or even damage to the strip. still stuck. The button has a small bar attached to it. that could be the cause or maybe the plastic power contact/strip that is under the button is warped and it cant make contact. if anyone knows for sure what is going on please let me know.
Answer to: Power and Lock Button Stuck, Requires Heavy Pressure