Freeware won't connect to Internet

I deleted some users from an XP laptop and now none of my freeware apps connect to the internet. IE and Outlook see everything, and I can navigate to new (not stored) pages using IE, but Firefox, Thunderbird, and Trillian cannot connect: “The connection was refused.”

I’ve never had this problem, and I had thought that my connection was closed entirely. I’ve been told that Norton could sometimes block freeware programs, but it hadn’t been blocking it before, and I actually deleted its registry “run” entry because the subscription had run out anyway. It doesn’t have an icon in the system tray any more, after rebooting.

I’d really appreciate bright ideas on this. Thank you.