Could be due to a few things. Go directly to the program folder & open the program directly. If it opens it means that your shortcuts are corrupt & should be replaced. If it doesn't open then try deleting your LW Preferences folder whilst LW is closed; instructions here: Fixes for Limewire

If those 2 things don't fix it, then uninstall Java & then re-install it. But downld the Java installer & save it to your comp 1st & then install it. Don't install Java over the net!!!