when loading sup sub editor, TinyMCE editor minify failing with "500 Internal Server Error"

With jscache off the editor works OK. But not with it on. The error only occurs when trying to load the OU sup sub editor. In pages with just the TinyMCE editor it is fine.

I purged my Moodle cache and cleared my browser cache and the problem still persists. I traced the problem to the parsing of the js in JSMinPlus. JSMinPlus::minify is passed the contents of tiny_mce_src.js and no filename. It throws a server error somewhere in the function where it is parsing the js. Can't figure out how to get the parser to throw an exception or output something intelligible to tell me what the problem is, all I see is ""500 Internal Server Error" in the Firebug net tab.