When I try to upload a file using the Flash uploader, I get an HTTP error. How can I fix it?
Flash apparently has a known (but not yet fixed) bug in the Upload header that causes an http error if mod_security is enabled. Some articles suggested that adding the following lines to your htaccess file may solve it:
SecFilterEngine Off
SecFilterScanPOST Off
HOWEVER, there are some who feel that is a SECURITY RISK, so you should discuss this with your web host before implementing any changes.
Here is an article that explains some ways to limit the risks to some extent:
http://www.askapache.com/htaccess/mod_security-htaccess-tricks.html