Out of the blue, I was receiving a red “HTTP Error” while attempting to upload images with WordPress’ core image uploader (WordPress version 3.6.x). This was occurring while using the mult-file uploader (ajax) and the legacy browser uploader. It even reported a HTTP Error while setting a featured image. There was a lot of users reporting this on WordPress.org, but I couldn’t find any solid answers. Here’s mine:
Make sure you’re running PHP 5.3 – as soon as I made this change, all 3 sites (including this one) started behaving normally again. You can make this change by adding the following code to you .htaccess file for each of your wordpress applications:
AddHandler application/x-httpd-php53 .php
Sidenote: I use bluehost as my hosting provider and the default configuration is PHP 5.2 with a single php.ini file. I did not change this setting in the PHP Config section of cPanel. I simply updated each .htaccess file in the root of each website. I hope someone finds this useful out there.