After a battery problem I now have a blank NAV screen. What happened: * The 540iT sat for a number of weeks and the battery went dead. Not realizing the battery was dead, I turned the key and, as you'd guess, nothing. * I charged the battery to around 70% (Sears charger with a readout) and attempted to start the engine. The battery could light the instruments but all lights flickered when I attempted to start the engine. The battery was bad. * Installed a new battery, charged to 90%, and started the car. Outcome: * Everything is fine except the NAV screen is blank. The radio works but I have know idea what I'm setting. The screen is alive only appears black. In the dark, I can see that it changes from completely off to a lit black. I've read a number of fixes including; removing the battery cables and discharging the voltage by touching the pos and neg leads together. This did not fix the problem. I've read a few posts that suggest reloading the NAV firmware. Their appear to be numerous versions of firmware available and varying feedback on the success rate. Have you experienced this problem and solved it? Any comments on downloading new firmware via a CD/DVD? Thanks for your feedback!