2) Telephone their support section & ask them.
1) A quick but not total test is to go here: http://www3.limewire.com:6346/ If you get the message saying Test page was successful then at least you can get thru port 6346 which is what LW uses by default. If you receive anything else then your port 6346 is totally blocked. In many cases with firewalls or modems/routers that use NAT, it only partially blocks this port. ie: you might be able to dwnld thru that port but nobody would be able to upld from you. Another test is to leave LW on for up to an hr & do this test: Bug Report instructions & sample image If it says false then there's something blocking LW's access.
Instructions to allow LW access for the most common firewalls can be found here: http://www.limewire.com/english/content/firewalls.shtml