I have a Windows VPS .
I have an SQL server on it running on a non-standard port.
All of a sudden I couldn't access it.
Seems that the Windows Firewall rules weren't applying. I turned windows firewall off.
Now it connects intermittently. It will connect, then it won't then it will.
I can connect ok from the server itself. It's something to do with the network between the server and the world.