Back to my Mac works perfectly at home between my mac pro and my MacBook. Each machine sees each other and screen sharing works flawlessly. However, when I have my MacBook at work connected to the internet, my Mac Pro does not show up in the Finder sidebar. Is this something that my company can firewall? Does Back to My Mac use a port number that is commonly firewalled? I can't imagine that IT has intentionally firewalled it since they (PC guys) have no idea what it is. So that's why I think that it's a routine port filtering thing. Anyway to get around this without involving IT? Like change it to port 80 or something?