After a lot of idle thought, i wonder if the original question is about network rendering. If that's the case then Vegas probably uses Windows network services which may or may not run over TCP/IP. It wouldn't use a port directly, but if it piggybacks over TCP/IP then it will may use port 135, but not necessarily.
Not really sure why it would matter. If local PC based firewalls are blocking it then most of them allow applications by name, not by port. If it's an internet firewall then one most definitely does *not* want to open the firewall to Windows network services as this would make the PC about as vulnerable as a naked baby caterpillar in a bird's nest.
Bob, true. But any firewall application should pop open a window saying "Vegas is trying to access the internet. Do you wish to allow it? Y/N". Which port it needs isn't something required.