As I said, what did the Bug report say? To be more precise, open LW, go to Tools->Options-->Bug Report. Click for an example. In the window that appears, scroll down to the part where it says: "Recieved incoming this session".
If it says false after that, then your firewall is indeed blocking LW's access to the Gnutella net.
Here's a link for general firewall configuration for LW:
http://www.limewire.com/english/content/firewalls.shtml
What do you mean exactly by intermittently? (Remember, not everyone is American or english...
)