firewall rules for google earth

[Luca Ferrari]

Hi all,
I've got an ubuntu machine that works as gateway for a lan of pcs, but I'm not 
able to access to google earth from anyone of the clients. The program says 
I've a problem contacting the server, but I cannot figure out what the 
problem could be. I've inserted a rule to forward the traffic from the lan to 
google.com, but it does not work. Any suggestion? 

Thanks,
Luca