[Scott MacVicar]

open admin/functions.php

look for

PHP Code:

    if (strstr($attachment,"..")!="") {
      //security error
      eval("standarderror(\"".gettemplate("error_attacherror")."\");");
      exit;
    } 


below add

PHP Code:

    if ($bbuserinfo["posts"] < 50) {
      //No Posting Attachments
      eval("standarderror(\"You don't have enough posts to post attachments.\");");
      exit;
    } 


replace 50 with number of posts they need to post attachments.