CofC Web Accessibility Guidelines- Rule (B)

(b) Equivalent alternatives for any multimedia presentation shall be synchronized with the presentation.

Translation: Any video or animation that displays crucial information should be captioned. The sound, video and text should all be synchronized.

What to do: Provide synchronized captioning for video or animations. Quicktime supports this, Flash does not. If you're using Flash, it may be possible to export the Flash movie as HTML and provide a link for disabled visitors.