There is a property for videos called "Auto Play". If that is checked, videos will start playing immediately.
Merely hiding a video does not cause it to stop playing. If you hid the video by clicking the eyeball, you just hid the video. You need to remove the video from all the states in which it does not exist. To do this, select the video in the layers panel, right-click, and choose "Remove from State", then choose a state. You also might find "Share to State > Current State Only" helpful.
yet again you guys "rock!!!"
By the way, I am working on improving "auto play" on videos for the next releast of Fc. In the next release you will find that a video with "auto play" turned ON will play when the video is added to the stage or becomes visible. In Fc beta II, auto play only works when the video component is created. This ends up corresponding to the first time it is included in a state. This isn't really useful since a video is often included in every state, but has it's visibility set to be different in various states. Look forward to this change in the next release...