For the last month or so my BB spontaneously begins "rebuilding message list" several times per day. when it does so, the screen turns white and a little clock appears and it is unusable for 5 minutes or so. when it finishes, it seems to restart itself, flashes a msg saying "verifying security software", and then resumes normal functioning. this is a HUGE problem if i need to send a msg or make a call urgently. why is it doing this??