Why do I keep getting interrupted by a Device Management - Software Update screen? How do I get rid of it?
That's very odd.  Normally there should be no auto-update of the device software, and other updates will require a reboot.  Try the following:


Hold both volume buttons and the power button
Wait until the phone reboots, keep holding
Release the power button about 1 second after the white text with your phone model appears onscreen, keeping holding the volume buttons
Recovery mode should appear
Select "Reinstall packages" or similar