Fellow inmates, I'm hoping that the collective wisdom here can help me resurrect my sad, dead Nuvi 550 . While updating its system software, I inadvertently powered it off during mid cycle (don't ask what on earth I was thinking at the time ) and killed it. It wont power back up; removing the battery does nada etc. And yes - the battery is fully charged. I am sure these units have a way to boot up the firmware through some diagnostic window by pressing the power button with some other screen touch combination - any ideas what that might be for the Nuvi 550? Much appreciated.