I have simmilar problem. At the beginning I will put some light on my case. I'm trying to do LiveCD of my system. To do this I'm using program called Ubuntu Customization Kit(UCK). During this program i chose option to add programs manually using console or software center. I chose console and i write in apt-get install name_of_package. I'm trying to install Meep. But I get this message: E: Unable to locate package meep
This works when I'm doing it on my system, but on console connected to UCK gives me this error. Any ideas why. This also worked few weeks ago on UCK but now it doesn't.
I've tried apt-get update but it didn't help. I think that it is worth metioning that I was able to install for eg. aptitude package.
Any answer which put some light on this case is welcom.