Your Modem/Firewall or possibly both got hit by a Spike on the mains and hung. All that should have been required was to unplug the power to them for 10 seconds or so and then put the power Plug back in and allow them to reboot.
Now what has been done here is that the Modem has been Reset so it's been returned to Factory Defaults and as I'm supposing you can connect to the Internet now your User Name & Password have been reentered.
But what you need to do now and here I'm assuming that you have both Wired & Wireless networks involved is you need to bridge the Wired & Wireless Networks together through the Modem/WiFi Access Point assuming that they are one and the same device.
What you need to do to accomplish this is to open the HTTP Address enter the User Name & Password and then make the necessary adjustments as well as configuring any WiFi Security protocols.
You can do this by either entering the CD that came with the Modem/WiFi Access Device and running the Setup Procedure though you'll most likely need to reenter your User Name & Password and then make any adjustments, or open the PDF File and find the way to enter the Setup Procedure and then open a Web Browser enter the HTTP Address and then the devices User Name & Password and manually configure it.
I personally prefer to manually configure these things and while I'm at it I change the Default Password to something different so that it can not be reconfigured over the WiFi Connection by strangers. ;)
As for devices that should be on your Network that includes all WiFi enabled Devices that connect tot he WiFi Access Point. There tend to be things like NoteBooks/NetBooks and WiFi Printers, and you may need to set a upper Limit on the number of Concurrent WiFi Connections to prevent strangers logging onto your WiFi LAN and stealing your Bandwidth. And devices that connect by wire tot he network are not required to be entered as these are safe, it's just any WiFi Connections that you need to set.
Also as the Modem/WiFi Access Point has been reset you'll most likely need to reestablish all of your WiFi Network again by rerunning the WiFi Setup Wizards on the devices. Any change to the base device will require all WiFi devices to be added tot he WiFi again.
Col
