In order for LimeWire to download something - there must be someone who can upload it. Not everyone shares files, so those who do frequently find that there is a lot of demand for their files - So while a search might find people who have the files, it doesn't guarantee that they have free upload slots with which to serve those files.

Also, if you are not sharing files then some clients will rarely let you have access to their files (such as me).

You could increase your success rate by only trying to download 4 star results (these had free upload slots at the time of the search).

Tools|Options|Searching|Quality

If you are behind a firewall and the person you attempt to download from is also behind a firewall this will also reduce your success rate in downloading files.

Mark