Conflicting firewall configuration can cause issues. I am not sure what OS you are on but try turning off the Firewall to be sure.
If that works, MS SQL Server default to TCP Port 1433. Try keeping that port open for incoming connections.
I have encountered issues in the past where there were multiple firewalls (Windows firewall, Norton Firewall) conflict and finally not allow servers to receive incoming connections.
Hope that helps.
Also make sure that you have restarted the SQL Server since you told it that it can accept remote connections.