After months of uptime (with occasional manual restarts), my RT-N66U locked up. Tomato Firmware 1.28.0000 MIPSR2-100 K26 USB VPN-64K.
Had the same problem some time ago with an RT-N16 running a DD-WRT release (since re-flashed).
Symptoms (RT-N66U, though they were the same for both):
LEDs normal. Will not route. No data in or out, via Ethernet or wireless. Could not authenticate to wireless. Responded to PING on Ethernet at its assigned IP address. Could not access web GUI to config. Could not telnet in. 30-30-30 made no difference. Resetting with WDS button DID work to reset to defaults. Operation prior to lockup was normal; nothing to indicate impending issue.
Pretty basic. Static IP on WAN. Static IP on LAN. DHCP off (except on VPN). DNS off (except on VPN). Wireless channels at defaults using WPA/WPA2 Personal with AES/TKIP. USB turned on with external storage for logs, but no printing. Minor non-complex access restrictions. PPTP VPN server. 4 lines of commands in startup init.
Comments? Pointers? What did I miss? Anyone else?