I am getting an 'HTTP Error' when uploading images to posts. What could be the reason for this? It doesn't happen all the time, sometimes I get the error, try again, and the file uploads. Actually the file always seems to upload, however it doesn't generate the different sized images or anything.
There a couple of different solutions depending on the cause of the problem.
In your case it seems that is not a upload problem. I would rather try adding the following plugin
This will change the default image editor