Post character limit ERROR

[Fingerprints]

Heya,

on our forum, once we do a post that is bigger than for example 3,739 words or 20093 characters (though the number varies sometimes, don't ask me why) the post completely disappears and nothing is shown. When you go back to edit a page all the text that was in it has disappeared too.

We have no idea what that is and are quite annoyed, because we need to post those posts up... even tried merging, etc, but it always leads to the same problem. Maximum characters per post is set to 0, which should mean we can do unlimited length posts? Is there somewhere else where it can be adjusted?

Thanks in advance!