Collector should use the same 443 port to connect to VC by default. I don't think I fully understand your environment, I would appreciate if you can submit a support ticket with detailed information about your configuration. Our support team will do their best to quickly solve your issue. You can submit a support case here: http://cp.veeam.com/
Is it possible that collector is running on a different server than Virtualization Extensions? In this case your NAT rule for extensions server may not allow other servers, such as collector server to access this "natted" port.