I had upgrade my blogs to WordPress 2.5, but i found that i can’t upload any image through the new AJAX image uploader. After i search through internet, i found this post, which teach user how to fix this problem.
I believe most of the WordPress 2.5 users will found this problem when try to upload image using the built-in image uploader, unless you use other blogging tools such as Live Writer.
Basically, this problem is due to the mod_security. The new image uploader has been rejected by mod_security. So, you had to modify the .htaccess file to disable the mod_security. This can be done to insert the code below to your .htaccess file:
This is just a temporary fix, i hope WordPress team can solve this issue as fast as possible. WordPress users, please upgrade once WordPress team release new version to fix this problem.