Might be a minor corruption in the firmware or an essential on-board file. Try first to load the original firmware again, use WebUpdater if it's still got Mass Storage Mode available. If no MSM then it'll be necessary to load an RGN file in preboot mode. If that doesn't fix it then use Cure firmware, kunix's QuickCure3 should work seeing its a nuvi 1490. Look for the link at the base of initial post here: [Only registered and activated users can see links. ]. Be sure to follow the instructions. Cure fw is necessary to regain MSM so you can re-format it with RMPrepUSB. Post again if you need more help or further explanation..