eXtplorer - PHP-based File Manager

Hi, I'm seeing this screen on all my Joomla! sites. It seems similar to a couple of others explained in earlier issues. I don;t see any error messages, but it keeps trying to refresh itself without success. Also clicking the link Return To Joomla does not return to the control panel. I have to close the tab to exit. I'm using exTplorer 2.1.7 under Joomla 3.3

I've used this program for years. I'm sure it's something I am overlooking. Thanks for your help.