Now would be the time to call Cisco support

But I'm assuming that you probably don't have a valid support contract at this point. SO...
Try reseating the memory and flash (although you would normally get other bad stuff if these were bad), remove all cards/WICs/whatever, and sit down and pray to whatever god you believe in.
Reboot it, if it works try putting in a card/wic/whatever one at a time till it doesn't work anymore. If one of them crashes it try to replace that card.
Also the console port could be horked, try the AUX port after the router boots up.
Report back your results!
--P.G>