Last week I had to unplug  my DIR-655 in order for the WIFI to work.  The computer hard wired to the router was able to receive internet service.  
This morning and I received the message "The DNS server is not responding".  Using Windows "Troubleshoot problems" did not fix the issue.  After rebooting the computer the internet worked again.
Do I need a new router?  Is "The DNS server is not responding" indicate a router issue or is completely unrelated?