Advanced File Manager and Error 500 on moduleinterface.php?

[pjb]

I'm using CMSMS 2.1.5. This morning I enabled the Advanced option on the file manager, and after that the administrative interface stopped working. Specifically, the banner and the left column of the admin panel appears as normal, but nothing appears in the main content area of the admin page, regardless of which item I choose from the left sidebar menu - e.g., content manager, file manager, module manager., etc. The main content area of the admin page remains completely blank.

Looking at the web console when I try to active the content manager, for example, I get an HTTP 500 error on the CMSMS file moduleinterface.php.

Any thoughts on why this could happen, and how to reverse it? Can I edit the database to reverse the Advanced option for file manager? How?

Thanks for your help.