@DJBlu are you using MSSQL on a multi-seat setup? I'm trying to test out MSSQL but I cannot for the life of me get my clients to connect to it! Are you able to send me your gentle.config for client/server so that I can compare if you are using MSSQL?
I was using MSSQL for multi-seat. Have you allowed TCP connections on the SQL server? They are disabled by default.
Also, I disabled the Windows firewalls, as I couldn't be bothered to configure them, and I run a hardware firewall on my router anyway.