What kind of problem and setup do you have? (Wireless addon adapter to the Xbox / DHCP etc...)
I did have a problem with another router (Watchguard firebox) and the XBOX360 Wireless addon adapter!
(The original MS one, there is a new one out on the market now, maybe it's better....)
The chipsets was not compatible with each other, so i did abbandon the XBOX wireless addon adapter.....
(The XBXO Wireless addon adapter did however work fine with the old DGL-4300)
Other things to check if you use wireless: use 802.11g settings on the router and the xbox!
(Remember the XBOX has wireless dualband 2,4Ghz & 5Ghz on the wireless addon adapter, but the DIR-685 only operates at 2,4Ghz)
Turn off WEP/WPA etc on D-Link settings and the Xbox during troubleshooting the setup!
Try to use a fixed IP/gateway&DNS setting on the XBOX, maybe the DHCP server died for you!
The firmware you want to use seems to be for the US version of the DIR-685, there is no update for Europe DIR-685 boxes yet if that is your setup/version.... (Someday maybe...)