I believe I found a small bug in action.denyforumaccess.php.
Around line 35 there is the line:
PHP Code:
if ($accessable['accessmask'] == '0') {
This should be:
PHP Code:
if ($accessable[accessmask] == '0') {
I found this out when I consistently received the "this forum is already un-accessable" error when trying to deny access to a forum for a user through the shop. I noticed another member in the thread (I forget his name) asked the same question, but AFAIK, was never answered. Now I can deny access to forums to all the users I want

. Hope this helps someone.