HTTP Error when uploading to WordPress

Hi,

When writing a post and trying to upload photos via ‘Add Media’ I get a HTTP Error.

The file itself uploads just fine, but there’s no thumbnail, no other data, and I cannot view it from the add media screen.

I have tried:

– Adding the mod_security information to wp-admin/.htaccess
– Changing theme back to default
– Disabled all plugins

But still no luck.

The photo I’m trying to upload is just 1.82mb and 4000×3000.

Running WordPress 4.2.7 on PHP 5.3.29.

Thank you