** MESSAGE TEXT MISSING FOR: TEMPLATE_FILE_DOES_NOT_EXIST ... event_detail_popup.html was missing.**
A missing template will cause an error however a proper error message should have been displayed.
That particular error message occurs after just upgrading to version 3.21 because a new messages.txt file is needed but was not supplied in the earlier upgrade .zip file (or the original messages.txt file should be edited to add an extra line - see the following link).
LINK > Topic: Error: Template File Does Not Exist when Adding Event
I contacted Matt about it quite a while ago. I don't know if he's updated the current 3.21 upgrade file to now include that file or not.
JFYI
Dan O.
[This message has been edited by DanO (edited July 04, 2005).]