In version 2.5.0 we have made some adjustments to the .htaccess Maker. If you are using this feature on your site we strongly recommend that after the upgrade of Admin Tools you go to Components, Admin Tools, .htaccess Maker and click on Save and Create .htaccess.
As noted in the release notes of version 2.4.3, there have been some changes affecting Professional users upgrading from version 2.4.2 and 2.4.1. If you are one of those users please note that due to a bug in version 2.4.2 and 2.4.1 the PHP File Scanner's settings were not being saved correctly. As a result, trying to run a scan –even after upgrading to the latest version– might not work properly. If this happens please click on the blue Configure button in the PHP File Scanner page and set the following file types to scan (one on each line):
php phps php3 php5 inc
Make sure the minimum execution time is set to 1, maximum execution time set to 5 and runtime bias set to 75%. Then click on the Save & Close button. This will allow the PHP File Scanner to work correctly.
This version requires PHP 5.3 or later. The rationale behind this is explained in our statement of mid-February 2013. It won't install on hosts running PHP 5.2 or earlier.
Unfortunately, due to a long-standing bug in Joomla!'s extensions installer, if your host has PHP 5.2 and you try to install the component on it the installation won't proceed but it will also make the Akeeba Backup icon disappear from the Components menu. You can still access the component by directly visiting its back-end URL, e.g. http://www.example.com/administrator/index.php?option=com_akeeba, or by uninstalling and reinstalling the previous version, losing all your configuration and data.
This is a Joomla! bug, not an issue with our software. There is no workaround. The other alternative would be letting the new version install but not work at all due to the PHP version incompatibility. We urge affected users to file a bug report with the Joomla! project.