fathopper Cox is known for filtering p2p, not everybody but they pick on individuals. And any p2p type. See ISP's known to BLOCK or Filter p2p or specifically Limewire

For others with problems try this if you're a windows user: Fixes for Limewire
And make sure your firewalls are properly configured for LW's full access: http://www.limewire.com/english/content/firewalls.shtml