What causes this message?
VNC Server has a 'blacklisting' scheme that blocks an IP address after five unsuccessful connection attempts. This is a security feature to prevent against DOS and Brute Force attacks against your Computer.
The IP address is initially blocked for 10 seconds, but this doubles for each unsuccessful attempt thereafter.
A successful connection from an IP address resets the blacklist timeout. This is built in to VNC Server and does not rely on operating system support.
How do I reset the timeout?
To reset the blacklist, you simply need to not attempt a connection for a short period of time, or restart the VNC Server software/the computer running VNC Server.
What username and password should I be using?
If you have failed to enter your connection details correctly a large number of times, it's possible they are not correct. Please ensure that you are connecting to the correct VNC Server, and that you are entering the correct username and/or password.
If you are unsure as to the username and password required, please see this article for some suggestions: What username and password do I enter when I'm trying to connect to VNC Server?