First thing to try is right-click LW & choose run as Admin. See if it opens. If not then reinstall all from scratch using this technique: http://www.gnutellaforums.com/333278-post2.html
(For Vista, both the installer & then the installed LW program should be set to run as Admin)

If still problems, check the topics here which might be the issue: http://www.gnutellaforums.com/genera...ta-issues.html