I have faced an issue of not having wordpress images to be crunched and the Media Uploader returns “HTTP Error” each time I upload an image. I noticed that even after recieving the error the image link actually works, but the thumbnail stays gray.
I have surf the internet searching for a solution in vain, and finally I have miraculously resolved the issue, and it has nothing related to the WordPress code rather than the PHP Configuration you are using.
For me I was using PHP 5.4 with a single PHP.ini file as a unified configuration, and after having the problem I went to my Host -> cPanel -> PHP Configuration -> Then Choosed [PHP 5.4 (FastCGI)]. Bingo! After that the problem of crunching has been fixed. Apparently the problem resides in the PHP.ini configuration and luckily enough by changing the PHP configuration the INI file has been updated correctly.
If you have the same issue and would like to comapre INI files, just post a comment.
I hope this will help people who might be astray.