Oh thank goodness. I was looking for info on this issue. I always use Software Updater, but since the 13.04 update for Lubuntu, I've had the same issue. When I run it, I get the "Failed to download repository information (check your internet)". But when I click the OK button, it goes straight to the next window, whether it be updates or the "No software updates are available."
I tried ping -c 5 http://us.archive.ubuntu.com/ubuntu/dists/raring/main/ && traceroute www.ubuntu.com, but I get the error.Code:ping: unknown host http://archive.getdeb.net/ubuntu/dists/raring/main/
Any idea what I can use to see where the errors are for me? I am running Lubuntu 13.04 on a Toshiba Satellite A135 laptop.