OK, that explains it :) With version 3.3.7 we are enforcing the check for PHP 5.2.7 or later. We have determined that Akeeba Backup will not work reliably with earlier versions of PHP, as we state
in our requirements page. When the module detects an incompatible PHP version it will disable itself. The idea is that if the incompatible PHP version causes the backup engine (which is loaded by the module in order to figure out if the backup is up-to-date) to fail with a fatal error, the module would take down your Joomla! administrator page. By disabling itself, it makes sure that this won't happen.
That said, PHP 5.2.6
was released on May 1st, 2008 which makes it three and a half years old. This is like an eternity for software! It was followed by 11 (yes, eleven!) PHP releases on the 5.2.x branch, all of which were solving
security issues which can be used to hack your site and your server. PHP 5.2 is already
end-of-life since December 16th, 2010. In other words, you are running seriously outdated, vulnerable software on your server. You have to ask your host to IMMEDIATELY upgrade to at least PHP 5.2.17 or, even better, PHP 5.3.8 - the latest supported PHP version at the time of this writing.
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!