A few days ago, I worked out how to implement "Premium Plugins," and I moved my installation of Simple Forum into my wp-content/premium-plugins/ directory after changing the hardcoded references to the plugins directory.
Today, I noticed that the author had released an update to it, so I upgraded and that's when I found this problem I'm experiencing:
When I have the plugin in wp-content/plugins, the link to the configuration page under the Manage tab works properly (the link looks like this: http://unsilence.com/wp-admin/edit.php?page=/simple-forum/sf-admin.php) and leads to the configuration page.
Placing the plugin into wp-content/plugins and changing the references to that directory in the code to wp-content/premium-plugins so that the plugin won't result in any 404 errors does not work. The link that gets generated is http://unsilence.com/simple-forum/sf-admin.php and following it results in a 500 error page.
I did some source-diving, but I couldn't come up with an answer after several hours. The author wants to look at the add_submenu_page() call, but I don't think it's the culprit.
Does anyone have any ideas?