"dns server isn't responding"

Hey all,

So last night I got back from a week long trip and one of the first things I did when I got home was turn my computer and the modem back on and I noticed that my computer was saying it was connected to the network but not to the internet. I then tried connecting my android phone to the modems WiFi and I had the same problem, the phone would say its connected but I wasn't able to open any webpages. I then tried the network troubleshooting in Windows 7 and I got the message "dns server isn't responding".

I've tried disconnecting/reconnecting the computer, and unplugging the modem for a minute but neither of these helped. Then this morning my dad rung our isp who couldn't find the problem from there either. The guy said that the dsl light on the modem should be constantly on, but it only flashes. he then went on to say that they can send out a technician to find the problem but if the fault isnt with the actual phone line then we'd be charged up to $200....

I've done a bit of googling and the "dns server isn't responding" error seems to be quite common, one of the only straight forward answers I could find though was to unplug the modem for 10 seconds which hasn't helped.

Any help would be greatly appreciated.