unable to activate JW player plugin for wordpress

I have the JW player plugin installed on my wordpress site but I'm receiving the following error;

There was a problem completing activation of the JW Player Plugin for WordPress. Please note that the JWPlayer Plugin for WordPress requires that the WordPress uploads directory exists and is writable. For tips on how to make sure this folder is writable please refer to http://codex.wordpress.org/Changing_File_Permissions.

I have changed the relevant permissions to writable (777) but the error persists.

Other users have suggested manually creating directory folder
wp-content/uploads/jw-player-plugin-for-wordpress
wp-content/uploads/jw-player-plugin-for-wordpress/player
wp-content/uploads/jw-player-plugin-for-wordpress/configs

These folders are already on my server and writable so that can't be the problem.

Is there another solution to my problem?

Thanks