The same thing happens sometimes to one of my clients using Invision Power Board. The first time it happened it was some kind of security settings that would filter some words. It was only one word that was being filtered but it was enought to prevent from posting the whole thing.
I believe it's the same thing in this case. The problem is not in the board or with the size of the text or copyright infringement. You have to take this to support and ask them to check the security settings. Attached the text so they can analize it and find out what word is causing the issue.
Good luck
