Clear user data loop

On the third dive today, Descent did not start "single tank dive" when submerged. Luckily, I wore another doc computer as well. However, the Descent restarted on its own and it shows"clear all user data?" on screen. Options are "no" and "yes" . Answering "No" looped back to the same screen. Answering "yes" it just stuck there.

Pressing light button for 15 seconds did turn it off but it shows the same screen after reboot.

What can I do to restore it to normal?