Based on this thread:

Quote Originally Posted by Gnoman View Post
Possibly on my end, but I've been getting this error message on Firefox intermittently for the last month or so.
and this thread:

Quote Originally Posted by LaZodiac View Post
Hello. Every so often, as of a couple weeks ago, when I've been loading pages I get an error message that reads as follows;

"Network Protocol Error

An error occurred during a connection to forums.giantitp.com.

The page you are trying to view cannot be shown because an error in the network protocol was detected.

Please contact the website owners to inform them of this problem."

There is a button to try again and this generally fixes it right up, but as it told me to contact the website owners I've decided to do... ergo this thread. So there you go. Seems like it could be an important thing.

I'm guessing that this has to do with the special character in the word Pokemon in the URL for that thread.