Trying to download software from the Ubuntu Software Centre the 'install' button for most of the software is missing and I get the following messages for various programs.
When trying to get ClamTK I get this message: "Available from the universe source."
When clicking on the 'more info' button of GIMP in the Software Centre I get this message. "There isn’t a software package called “gimp” in your current software sources."
I have gone to system settings and opened software and updates under the tab 'Ubuntu Software' all the boxes are ticked. In the 'Other Software' tab the first box isn't ticked (CDROM with Ubuntu 12.10...) but all other boxes are ticked.
Can someone please explain what is causing this and how I can go about fixing it?
I reinstalled 12.10. I then upgraded via the CLI to 13.04. I have reinstalled and upgraded from 12.10 to 13.04 many times and never come across this.
Thanks in advance.