It seems many folks are running into (or have ran into) a problem with the flash media uploader in Wordpress 2.7.1 and 2.9.1.

Here is a basic fix for the HTTP Error message you may be getting when trying to upload images via the flash upload.

  1. Edit your .htaccess file, which is located in the ROOT of your Wordpress installation.  Not your theme, not your main http root.
  2. Add the following lines, save and reupload.
    #BEGIN Image Upload HTTP Error Fix
    <IfModule mod_security.c>
    <Files async-upload.php>
    SecFilterEngine Off
    SecFilterScanPOST Off
    </Files>
    </IfModule>
    <IfModule security_module>
    <Files async-upload.php>
    SecFilterEngine Off
    SecFilterScanPOST Off
    </Files>
    </IfModule>
    <IfModule security2_module>
    <Files async-upload.php>
    SecFilterEngine Off
    SecFilterScanPOST Off
    </Files>
    </IfModule>
    #END Image Upload HTTP Error Fix
  3. It might help for you to delete the remote .htaccess file before trying upload the new one.
  4. Make sure you keep a backup of the original just in case.