There are lots of infected files being shared on the network. It's just as easy to download an infected file with LW Pro as with LW basic

Make sure that you have a good, updated AV & scan files that you've downloaded before you open them! If you don't have an AV, have a look at the link below.
http://www.gnutellaforums.com/264170-post2.html

Also
WARNING: Viruses on the network you should be aware of

Sorry, I forgot to include the link for deleting the prefs folder. If you need to do that in future, see points 2 & 3 of the link below. If you've used older versions of LW in the past, there could be a folder in either location.
Fixes for LimeWire
Deleting that folder will kill all of your settings within options...you'll haveto go back through afterwards & reset your options.