Yours can probably be fixed with the same "uninstall and reinstall" of the community sources. What happens is that some sites change their site information or the names of the files that they provide on their repository. The default Community Sources file in Installer has the information that was current at the time Installer was released. Since these changed after that time, removing the community sources and then reinstalling it loads the latest version with the most current source information for the files you are looking for. Some will still work with the old community sources but ones that have changed with result in a package download failed or host server unreachable error.