Had the same issue where in the internet would stay on and then off and few minutes later on again. Only solution at that time was to do the ipconfig release , then renew, and then have WIN 7 do its diagnostic work
..all went well again and then after awhile the same process repeated.
Went to the OpenDNS with the 220 1st and the 222 2nd. That worked for a while but the DNS issue came back. Changed the primary and secondary to 222 and 220 and that seemed to work for a while.
Finally did an upgrade to my WRT600n router with DD-WRT and kept the last OpenDNS settings and have not had the issue since.