There are oh so many possibilities...
Originally Posted by samsmic
1. Can you telnet to the remote server on the correct port?
2. Is there another firewall at the other end (I assume so since it's a VPN)? If so, can you verify that the traffic is getting beyond that firewall?
3. Are both firewalls set to handle the "hand-off" that occurs when incoming traffic on port 1433 is handed off to a negotiated port? This is usually automatic, but on some older firewalls, it must be manually configured.
4. Are you using hostname or IP address to connect? If hostname, what is the name resolution service running (I assume DNS)? If DNS, are you sure about the IP Address resolution?
5. Are you NAT'ing the internal IP addresses? Are the NATs configured correctly.
Look at your firewall logs carefully (hopefully there's a nice GUI to help you). The answer is likely in there somewhere. It may not be easy to find, but it's in there.
Have you hugged your backup today?