GPSMAP 66i - Suddenly turns off

I have a GPSMAP 66i. I have it updated with the last version 8.80. I have some problems lately.
a) When I am changing pages and I get 'Recording Controls' sometimes (no pattern I found) suddenly freeze the screen (any buttom works) and inmediatly the device switch off.
b) In two times, during a navigation when I go to 'Recording Controls' and then into the thrid option (at the top of the screen, -current activity-) the arrow to pan does not move on the screen.
Could anyone help me? Thank you very much.