sorry to bump such an old thread...but I just wanted to say that this advice fixed a problem I might have had for a long time. People have complained that they had difficulties posting from time to time but it seems that most people with this problem simply gave up and decided just to go away
Then tonight a friend of mine tried to post and got the "The host you are trying to send the input from is not a valid host" message. At first I had no idea what was wrong, then I desided to search for it here and voila! I found this thread and the problem was fixed in a minute!
