Thanks for the reply. Hm, interesting. Seems like when my camera crashes it's when I'm in MF mode where my shutter release is the shutter button and my focus is set to the Movie record button. I had a feeling it was that combination. The dive after my camera crashed, I set my camera to S-AF where shutter release button was for the shutter release and focus (half-pressed). No crash on second dive.
When your F1 button was set to shutter release, did you have a separate button set to focus?