This ended up being a bug which I've corrected in your installation. It's a simple fix for anyone else that might happen to read this post.

File in question: scripts/showflat.inc.php
Line # in version 7.5.5: 950

Current Code:

PHP Code

$userstatus = $html->user_status($usernum,$gimages);

New Code:
PHP Code

$userstatus = $html->user_status($usernum,$gimages,$modcheck);