Ubuntu help please.

I'm running ubuntu on my laptop, and when i try to add new programs to it with add/remove aplications i get a message saying

The list of applications is not availabe

Click on 'Reload' to load it. To reload the list you need a working internet connection.

then i click refresh/reload, it does so then when i try to add something the same thing happens. I am connected to the internet, fully updated, everything else works except for trying to add/remove programs. I am using version 7.10(gutsy gibbon) of Ubuntu.

try "sudo apt-get update" in terminal

i had this problem also when i used 7.10 ubuntu. if that does not work, try going in to snyaptic package manager. i think it may give you a command to use in terminal to fix the problem