Ok...this one is not so difficult. It happened to me several times and this is how I fix it when the problem arises(and it does alot). Uninstall your existing limewire.Then go into your c-drive and delete the remaining limewire file-there will be one left behind.You will find it in "program files". Additionally, go into documents and settings and delete the limewire file there(remember to save to disc any movies or music first).
Now...download a fresh version of limewire,but before you install it save a copy to disc(for when you have to do this again-and you will...eventually) then install .As it installs you will be asked if you want it to run upon finish of install. Uncheck that box. Then after install "run as administrator".
That should help you. It works for me
Good Luck
Cobaltazule