That’s a really odd error, the URL looks like a reference to an Eclipse 4.5 update site (7+ years old) which we don’t actually serve (will be doing some additional testing there). From your previous posts, I know you’re on a recent MyEclipse version, which uses a far more recent Eclipse version too, so the reference is odd – unless this is another older installation?
1) How do you get to this dialog – Help > Check for Updates?
2) Can you check the URLs listed in Preferences > Install / Update > Available Software Sites – if this URL is there, delete it. You may want to restart MyEclipse and then repeat the check.
3) Please send us your entire workspace error log.