Despite what McAfee says, make sure Windows firewall is turned off.

Remove the previous firewall rule from McAfee & re-add it. Some firewalls are like that, an update of either the firewall or LW software means the the rule needs to be re-added afresh.

Other than that, try a combination of these steps, such as replacing the gnutella.net file: If LW Will Not Connect (click on the blue link)