EDIT: I missed your point about you using a mac. Which operating system version are you using? eg: OSX 10.3.9

1. Do this simple test for us. Using your browser go here: http://www3.limewire.com:6346/ The page should say 'Your test worked!'. What happens when you go there?
2. What firewalls you have?
3. How much ram?
4. Hard Disk space available?
5. Connection type? (eg: dialup, broadband, cable, etc.)
6. Modem & router brand name & model numbers?
7. Where are you trying to connect from (home, school, work, etc.)?
8. What version of Limewire (LW) do you have?
9. Who is your isp provider (Internet Service Provider)?
10. Are you sharing the connection with other computers or p2p sharing programs? If yes, please give details of set up.
11. Is this a your 1st try at LW or is this a new problem with an experienced user.