Have I read the related troubleshooter articles above before posting (which pages?)? Yes
Have I searched the tickets before posting? Yes
Have I read the documentation before posting (which pages?)? Yes, Installing Admin Tools
Normal installation
Joomla! version: 3.1.4
PHP version: 5.3.24
MySQL version: 5.1.70
Host: (optional, but it helps us help you)
Admin Tools version: 2.5.3PRO
Description of my issue: It is similar to here:
https://www.akeebabackup.com/support/admin-tools/16906-403-forbidden-error-2-2.html
Essentially, this URL gives a 404:
administrator/index.php?option=com_admintools
It looks like this: http://monosnap.com/image/lApitIyxYFkQKEadPIxUbfGvH
Restoring the default HTACCESS, disabling the Admin Tools System plugin or setting the error reporting to NONE did not solve the problem, nor did uninstalling or re-installing Admin Tools.