Hi, this suddenly happened to me in the middle of the afternoon today. I have a DIR-655, hardware version B1, with 2.11NA firmware.
I suddenly lost connection on my machine (and all other machines in the house), including my mobile - I'm posting from that at present, so I'm sorry if the formatting here leaves something to be desired.
Anyway - I restarted the router remotely at first, connecting thru the browser admin panel, as this usually fixes things. This time, it didn't!
Thinking it a bit odd, as nothing was wrong with the network configuration/dhcp settings, I checked to see if the router itself could connect to the Internet using its ping tool, and it could!
Thinking this a bit odd, I power cycled the router and modem to no avail. The router could still ping the outside world, but all the machines connected to it were out of luck. Connecting directly to the modem also lets the one machine connected access the Internet, but that's not exactly a tenable solution.
Searching for "router can access Internet but computer can't" was pretty fruitless, so I'm posting here now. Literally nothing has changed in my router's settings between the instant it was working and the subsequent instant it wasn't. Power cycling and restarting does nothing, for router, modem, and computers alike. Wired and wireless connections are equally non-functional thru the router. So, uh...
What caused it to mysteriously and suddenly stop working?