Ever since I upgraded to WordPress 2.5, I have been having problem with images uploading. I have not been able to upload any images and what it shows is only a ‘HTTP Error‘ message, without any further details for the user to debug the problem.
After some research, it seems that the issue lies with the mod_security. To fix it, simply paste the following code
to you .htaccess file. The flash image uploader should now work.
If you have tried all method and the image uploader still don’t work, then grab the plugin Flexible upload. This should work the trick.