If you can ping other sites (like freerepublic.com) by number, but can't ping your DNS servers by number, then they went down. Contact your ISP or whomever runs them. All but the most incompetent ISP will be well aware of any such DNS server crash. You need at least one DNS server to translate the human readable URLS (such as freerepublic.com) into numeric IP addresses (such as 209.157.64.200).
If you can ping at least one of your two DNS servers (most folks have two) by numeric IP address, but not ping any site by name, then the hardware system that runs the DNS server software is up, but for some reason (difficult to debug from here) you aren't able to use that service, perhaps because that DNS server software isn't running on that hardware system like it should be.