"unknown category" - error and white screen of death error
If moodle gives you an error called 'unknown category' and / or goes blank, this is the fix:
cd /var/www/html/moodle
pico config.php
look for the line that mentions a theme:
$CFG->theme='boost';
put a hash mark in front of it, like so:
# $CFG->theme='boost';
this line in the config file basically forces moodle to use the default theme.
discussion is here: