Hey,
Ran into the same issue… did troubleshooting for the last several hours until I finally landed on the post thumbnail section in my functions.php being the issue. I wish I had a complete solution here, but I don’t, and I’m wondering if for some people if it’s a bug with their theme, or something that is messed up in WordPress 3.5.1…
Let’s just say I did the most common sense things that are told to everyone on how to solve problems… ie deactivate/activate plugins, re-install the version of wordpress, etc. I went through and checked my javascript and jquery that I have manually installed (deleted the enques, uploaded image and got the same result as always: http error).
I figured it’s something to do with my theme because the 2012 theme works wonderfully. Finally I deleted everything in functions.php. I then uploaded an image and it worked perfectly. From there, I went through trial and error of deleted each different section and then uploaded an image, but to no avail, still the same “http error”: jquery, navigation, sidebars, shortcodes didn’t work, until I got to post thumbnails… and this is where I am now…
here is what my code looks like (this is what I believe causes the http error for me):
// Featured Thumbnails
add_theme_support( 'post-thumbnails' );
set_post_thumbnail_size( 210, 210 );
add_image_size( 'featured', 260, 260, true ); // Located on FRONT PAGE
add_image_size( 'quicks', 160, 160, true ); // Located on FRONT PAGE
Because when I take away the “true” in the add_image_size, everything uploads fine and no error.
// Featured Thumbnails
add_theme_support( 'post-thumbnails' );
set_post_thumbnail_size( 210, 210 );
add_image_size( 'featured', 260, 260 ); // Located on FRONT PAGE
add_image_size( 'quicks', 160, 160 ); // Located on FRONT PAGE
The solution of taking out the “true” would be fine if this was just my site, because I don’t mind cropping images to fit properly, but I don’t expect any clients to do the same. I’d much rather them be able to upload an image of any dimension and have wordpress crop it for them… isn’t that what makes wordpress (and other CMS’ special?).
I’m wondering if this is the same issue that you guys are having, and if there have been any luck finding solutions. Would love to get to the bottom of this.