Also I would like to say that, what you are facing isn't a result of default setting or user-mistake setting of the Flash player version you have. If its done, its likely its done on purpose by your system Administrator who wants to prevent file uploading.
There is another option
FileUploadEnabledDomain=FQDN or IP of your WFA server.
This will allow File uploads ONLY for your WFA server and prevent the rest.
If this post resolved your issue, help others by selecting ACCEPT AS SOLUTION or adding a KUDO.