Rather than running without a firewall (dangerous), turn on Vista's firewall & make sure that the firewall's allowing LW.
Check out the thread here:
If LW Will Not Connect
There are lots of fixes to try & links with info about configuring firewalls etc. First fix to try is deleting/replacing the gnutella.net file. If that doesn't work, delete LW's preferences folder. If that doesn't work, go through all the other fixes.
If nothing there helps, post back with your system details (see for thread for more info about the details that we need)