I am having the same issues with LW 4.12.3 Pro. I've installed on a new PC with cable connection. Searches are fast. Many songs have 3 or 4 stars with numerous users. The file sizes look to be correct for the bit rate. I've had LW fo a long time and never experienced this before.
I can click to download but the entries say "need more sources" or they will try to connect but seldom do. Occasionally one will download but this is rare. I've even uninstalled and reinstalled several times but that doesn't seem to change anything..

The only way I've figured out to bypass this annoyance is to search for a partial artist name. Obviously with U2 or Prince you can't, but if you will search for "furtado" instead of nelly furtado and "faith" instead of faith hill it seems to yield reliable results. Sometimes if it keeps generating bogus results I just search for the song name and not even put the artist name. That usually does the trick but it's still a pain.

Well, I got the file to download no problem and I have the new LimeWire 4.12.3 so maybe it is getting better.

Brandon