You have now double-posted, triple-posted and cross-posted

None of these are tolerated in these forums and the effect is actually opposite -- you may get ignored. Please stay in one thread and use the

button if you have new information and nobody has replied yet

I do not have any experiences with Macs and it seems that you have already checked almost everything possible without a success. The only thing I can do is to create a checklist for you, just a list of things you may give some attention and double-check that everything is right.
1) Does the
data/servers.xml file contain the right server name and port number?
If you have modified that file (for example, you may have tried to run a local server), do you select the right server from the list when running Planeshift?
2) Do you have a software firewall running on the same machine that you use for Planeshift? Could that firewall or any other software possibly block outgoing UDP traffic on port 7777?
3) Could your Internet router/gateway/firewall possibly block outgoing UDP traffic on port 7777? According to
DaveG, some firewalls allow support both
bidirectional and
unidirectional UDP. You need
bidirectional UDP.
4) Could your ISP block UDP traffic? Some ISPs may do it in order to block file sharing programs and force you to buy a more expensive package if you want to use corporate VPN connections etc.