After careful debugging this problem we found out that this is not a bug in SmartCode VNC Manager. VNC server has a protection against brute-force password hacking attacks. The server uses a time interval in order fight brute-force attacks and it enforces a time gap between authentication attempts. In case if you receive 'rejected connection' message, you must wait a little bit (20-30 seconds is enough) and after that try to establish connection again. If the problem persists, you may try to restart VNC server service. This will rest the VNC server blacklisting rules.