If you have PeerGuardian* installed, it could be blocking the downloads, but more likely is that a lot of those returns (Eg 90+ ) don't actually work. If the "browse host" button is greyed out, that is sometimes a clue.
I've found, sometimes, that it is better to try and retrieve a song that only one IP address is hosting. Might take a little longer, but it often works.
If this happens with every single thing you are trying to download, it's likely to be a firewall (yours) that's blocking it.
Any particular mp3 you're trying to download? If I have it, I'd happily send it to you.
* Peerguardian is a fairly popular program designed to block access from blacklisted sites. The blacklist is made up of a number of different categories, including advertising, spyware, the music industry mafia, etc. It's somewhat effective, and you can add user-specified addresses to the blacklist.