Maybe my problem another... My device doesn't start after I have installed one software (I don't remember which) When I turn on it, blue indicator light up, splash screen "Nokia" appears, then blue line goes to end and... device hang up. Don't answer any acts. With power and swing buttons pressed start in usb mode didn't work... but I didn't know work it with inserted usb cable in also, I didn't have test... Then, I make next:
I remove battery, plug in DC adapter, press power and swing buttons together for 3 sec. Plug out Dc power, insert battery back. Start up software update wizard at computer, mount usb to my device, press power and swing buttons again.... on the screen appears USB logo, computer recognize device, and I began update. After all my N810 works again, but I lost many data after update, but that is small cost for good emotions!

Don't forget to charge battery at full before update!!!
The most better choice is Official Nokia help services, another might be is danger!
Good Luck!