In my installation of 7.2.2 under Linux this problem was caused by the hidden input ocurl, which is part of the form submitted by the Board Rules acceptance-getting page, not containing the port number of the server, thus, in the source of the page:
type="hidden" name="ocurl" value="http://www.curriculum.org/mboard/ubbthreads.php?ubb=cfrm"
needed to be:
type="hidden" name="ocurl" value="http://www.curriculum.org:8880/mboard/ubbthreads.php?ubb=cfrm"
ocurl is composed by the function give_rules, defined in UBB_HOME/libs/ubbthreads.inc.php
In this function:
$ocurl = "http://" . $_SERVER["SERVER_NAME"] . $_SERVER["REQUEST_URI"];
where $_SERVER["SERVER_NAME"]
returns the name of the server without the port#
I noticed that in my config (see UBB_HOME/includes/config.inc.php) the element REFERERS contains the correct value (with the port#, and also "http://", so I changed the assignment to:
$ocurl = $config['REFERERS'] . $_SERVER["REQUEST_URI"];
This assignment, using a literal, also worked:
$ocurl = "http://" . "www.curriculum.org:8880" . $_SERVER["REQUEST_URI"];
This solution may not apply to other systems that are exhibiting this problem but it may help you to figure out what is needed in your case.
If there is a better solution to this problem I would like to hear about it so I can patch my installation accordingly.