I'm doing update and maintenance on a Joomla site that hasn't seen much care for the last year or so. When I log in as an administrator I can only click around for a few minutes before all the links start going to the 404 error page (though one time I got the 500 Error after clicking Manage Users).
Other clues I've been tracking include:
- Once the 404 problem starts up I can get back to the initial admin panel page (i.e. http://domain/administrator/) and CNTRL-F5 and not get a 404, but all the other pages are using query strings and remain inaccessible
- Turning off SEF URLS and URL Rewriting didn't make a difference
- After the 404 issue starts, the Maintenance section says "Unknown Joomla" and "Unknown Extensions"
- the problem existed when it was Joomla 3.4.0 and persists since it was updated to 3.5.1
- It looks like the site dates back to the v2.x era
- The preceding seems significant because the front end is using Yootheme's Mustache template and it looks like that theme was not updated to work with Joomla v3.x