Error: Reliable Channel Overflowed - STEAM

If you are getting Reliable Channel Overflow messages this suggests one of the following issues:

Your internet connection or the server's internet connection is having problems.
You have some P2P or similar program running on your system, sending email will also cause this.
There are other computers on your local network using your internet connection.
The server you are on has its network connection overloaded (too many players or it's sending email or something).
You are running on a wireless connection.
You have a Virus or Trojan or Internet Worm infection that is generating traffic.
You are connected to the internet using an analog (56K) modem.
You have your rate or cl_updaterate or cl_cmdrate settings too fast for your internet connection.