I'm getting the minimum number of character bugs too. It's something to do with the change needed to this in SHOWTHREAD, newreply and newthread
Code:
<form action="newreply.php?do=postreply&t=$threadid" method="post" name="vbform" onsubmit="return qr_prepare_submit(this, $vboptions[postminchars]);" id="qrform">
Where qr_prepare_submit is replaced with fb_qr_prepare_submit
There's some kind of bug in that code

Note i'm running 3.7