MP4 not working on iPhone & iPad

Hi,
I love this plugin!
My FLV videos work fine on desktop webpages, however I cannot get the .MP4 video to work on the iDevice. The video appears with the Play button in the centre of the black video rectangle, but the Play button has a line through it, to indicate it cannot play.

Any help much appreciated. cheers Tricia

http://wordpress.org/extend/plugins/stream-video-player/