I was running in the same problem Morrus did. In the meantime I?ve found out, that this error occurs when the max. length of usernames is set. Mine was set to 25 and resulted in the error message, that the username would be to long.
Somehow AGP&R seems to check the textbody in the replybox against the max. username length.
But to make it more complicated: I?ve changed the max. username length to 35 characters and you know what?! The bug is vanished. At least for the moment.
May be anyone can confirm this for his sites?
My ole man always told me "If you can?t understand it, behave like you would love it." Okay, he was talking about women in general. Guess until John comes up with a bugfix I?ll keep it that way