I have a similar problem, but my ubuntu updates are working fine i think, as i can install packages without problems and apt-get update gives no errors, but when i
or any other PPA i get
sudo add-apt-repository ppa:webupd8team/y-ppa-manager
As i´m able to post this, my internet is working fine and i´m on ubuntu 13.04
erik_ubuntu@Erik-MacBookAir:~$ sudo add-apt-repository ppa:webupd8team/y-ppa-manager
Cannot access PPA (https://launchpad.net/api/1.0/~webupd8team/+archive/y-ppa-manager) to get PPA information, please check your internet connection.