Have you tried uninstalling and reinstalling Fring? Have you looked at the Fring support forums to see what other people say about this error message? (Maybe it's a common/known issue and someone will have reported what worked for them). I would also say check your settings, but it sounds like you haven't even gotten the app to start up yet.

I would probably try those two things first, since other apps can hit the web but Fring can't, I'm tempted to blame Fring (or at least your version/installantion) first. Lots of us on here have used Fring and no one here has mentioned that problem before. If reinstalling and searching the Fring forums don't get you anywhere, then try Entourage tech support. But I'd do at least those two things first, if it were me.