If the amber leds blinks when you press the front or reset button, then alt-f is working and you have a network problem.
If the router says the box has an ip but your network scanning don't show it up and you can't ping the box, then probably the router is retaining an old lease, try shutting down the dns, reboot the router, and see if it stills shows the IP lease.
Notice that the "connection time out" message is not the same as a "Connection refused" or "No route to host" or whatever putty says on a non-existent IP.
As a last resort you can try a direct-cable PC-to-nas connection. When booted without a DHCP server, and if no static IP is setup, Alt-F will use IP 192.168.1.254. Search the forum for this.