I dont know whats the problem but it seems after every fresh installation of ubuntu in any device (have started noticing this problem since ubuntu 11.04) the connection to the software sources are down. I cannot download any software from either apt-get or software center. Also i cannot use the Universal Source for packages like chromium, etc. And then suddenly after a few days, the mirrors are back up again!! Its normal back again! I dont know what the problem is, but it happens every time. Is there any solution to this or we just have to wait for a few days till the mirrors are back again? (and I have also tried changing the download server, It doesn't helps!)