Maybe you forgot to add the last slash ( / ) in the URL for repository. I think they are mandatory. Then if you added more repositories at once and problems still persist you could try to activate them only one by one with the checkbox option you are offered.

Bye, Val.

P.S. Once your repositories are set up you should make a manual backup of your /etc/apt/sources.lst (hope it's the right filename), the included backup program doesn't do that for you.

Bye, tira.