Samsung a570 Phone will not stay on. It is fully charged, and comes on briefly, but shuts itself down immediately. There was no mishap involved (not dropped, did not get wet, etc.) Phone started doing it a couple of days ago for no apparent reason. Have tried removing battery, and have tried it with a working battery from another a570, but no go. Have had it for a little over a year (2 year contract, warranty for phone expired at 12/23, of course!) Any help appreciated.