Redownload from here
http://www.limewire.com/english/content/download.shtml
If you're a pro user, then get it from your personal pro page.
I'd recommend backing up your complete incomplete folder. Then after reinstalling LW, close it, then replace the incomplete folder with the old one. But this must only be done whilst LW is closed.
Oh & you should also backup all your previously downloaded & shared files.