site running Joomla 2.5 - see here - metrotechnet.com - site was fine for 2 days but now is a blank page. Getting error 500 & 504. Could it be a PHP.ini setting? Can I disable the security component to see if that resolves it?
My apologies, this wasn't Security Pro Center, it was the security pro app for Joomla 2.5. To install it I had to upgrade my PHP version to 5.3 That seemed OK. I later changed the permissions as recommended. Everything seemed OK but I wonder if I was working with a cached version of the site & wasn't seeing the live site after the changes.
Despite I don't provide support for J25 branch, the extension was fully tested and worked fine meanwhile that branch was active (and nothing has changed since then). If it was working after installing it then it should work always; cache doesn't affect when we talk off a 500 error.
Try disabling the extension and also ask to your hosting provider; it will be able to give you a clue of what's happening.