Thank you guys, after a long search I found this topic with very useful links...

I had the same problem, one particular song that I couldn't download. I thought something was wrong with Limewire so I re-installed two times, did countless checks on my connection until I thought... Let's try to download another song ! That worked perfectly so I was sure Limewire worked properly. I then started looking in the forums, but there are so many subjects !!! But after one hour I ended up here, and now, by looking up via the album name instead of the songs name I succeeded.
I also fine-tuned my Limewire with some of the tips I found under these topics.

Thank you all !!!

Michel