I've had a few reports since releasing version 0.26 of Radio Downloader of it being removed from people's machines by Norton Antivirus due to it having a 'low reputation score'. I'd like to take the opportunity to reassure you that Radio Downloader is still perfectly safe. The installer and binaries are signed with my personal code signing certificate to prove that they haven't been tampered with, and the full source code is of course also available to download to prove that it doesn't contain any nasties!
Unfortunately the way to get Radio Downloader whitelisted by Symantec (the author of Norton Antivirus) appears to be for me to fill out rather a large form on their website and then wait several weeks for it to be approved. As I'd rather spend my limited free time improving and supporting Radio Downloader instead of doing Symantec's job for them, I've decided not to do this for the moment.
If you are being affected by this issue, I'd recommend uninstalling Norton Antivirus from your machine and replacing it with the free and excellent Microsoft Security Essentials, which I have been using for years and would recommend most highly.