I assume that when you say you payed for the pro version and it didn't work -- you mean you couln't download anything. If this is the case then it is not a problem with limewire but the nature of the gnutella network itself.
With the content on the network changes rather quickly it is not impossible to see hits for your search but the files not be available. There are a few things you could try to overcome this situation.
a) try to limit your downloads to 4 star hosts
b) do multiple searches for the same content.
c) kill any downloads that do not immediately start to transfer.
d) make a note of machines that return results and aburptly disconnect you in the middle of your transfer.
Try to avoid downloading from hosts that constantly return results but disconnect you when you try to download from them.
hope this helps.
http://www.leeware.com (FSP)