it basically means that the person who is hosting this file as gone offline, and limewire is having trouble finding more hosts (aka sources) to download from. a good way to void this is to pick the ones that have the most sources, available. also use bitzi to check if the file is what it says it is, also give info about the quality too. be sure that the (connection/queue) quality rating is atleast four stars, if not, you may have trouble getting the download to start.

you can also click/highlight the file in the download pane and then click resume/find sources. this wil make limewire try and find sources for you. you can also do your own search and if limewire find the same sources in the search pane, it will start downloading from that source.

good luck