Lots of people have had trouble with McAfee.
A lot of people have uninstalled McAfee (or parts of).
http://www.gnutellaforums.com/showthread.php?t=66843

But this poster found a solution & is now able to run LW with McAfee
A fix for Visat/Limewire

See if that helps. If not, you might need to configure your modem/router. In that case, we'd need the details.
Have a look through those threads first though, see if McAfee's your problem