OK, I just confirmed in my lab environment that if the default gateway is NOT correctly setup, then you get the exact same two symptoms that you have described above.
a) Following error in Control Center when you try to register the license
Cannot register the specified license file.
Unable to communicate with Symantec to register. Please check your connection settings, and try again. Connect failed; Operation now in progress
b) Telnet to register.brightmail.com on port 443 from the appliance attempts to connect to both the IP addresses of register.brightmail.com host and times out:
Trying 216.250.24.63...
telnet: connect to address 216.250.24.63: Connection timed out
Trying 143.127.103.14...
telnet: connect to address 143.127.103.14: Connection timed out
Please note that you would get these symptoms when the DNS server(s) configured on SBG are on the same subnet as the SBG because in this case the appliance is able to resolve the hostname (of register.brightmail.com) using the DNS server(s) located on the same subnet.
Unfortunately, there is no way to change the default gateway at this stage without first registering the appliance (which obviously is a catch22 situation). So you would have to use "clear all" command to reconfigure network settings ensuring this time that the default gateway is configured correctly.
Hope this helps.
Thanks
Adnan