If they are older torrents, perhaps nobody is online at the time you are attempting to connect with those torrents. LW's torrent abilities are limited unfortunately.

If you really prefer to persist with LW for torrents, get LW 5.2 or even the beta 5.3. LW has made some small improvements in their torrent implementation. Download LimeWire 5.2.13 - Lime Wire _ or _ http://www.limewire.com/download/betaversion.php