I just set up two Macs with Coccinella 0.96.4 and Jabber accounts. After browsing the preferences, I found that Coccinella want some open ports (General > Network > Ports), so I opened them on both sides (UDP and TCP as the preferences are not specific on which type of port Coccinella wants). I also activated NAT on the other tab and let Coccinella detect the external IP.
Then I tried to voice chat, which failed - no matter from which side I initiated the chat - with the error:
"Either you have a rigorous firewall or the other user has one that does not allow network connections like this".
Text chatting works fine though.
By the way: Voice chatting _inside_ the LAN works.