Actually, I had this happen to me as well. Both my hero and DK were in stealth mode when I returned from one of the battlefields. I had NOT been in stealth mode when I left the battlefield. I tried everything, including above tip, but nothing worked. I am positive it was some type of game glitch. I had saved just prior to warping from battlefield (you are nuts if you don't always save before jumping back and forth). I then rebooted my computer, went back to last saved game, and then warped out of the battlefield. Everything was fine then, so try that if it happens again.
