Thanks for the reply,
The letterbox is a crazy red white and blue creation made in our design department. Otherwise I would just use the Avid one. I have re-imported it and got the same error. And here’s where things get even wackier. The video is 3 segments, so I’ve made 3 timelines. All with this same treatment. Timelines 1 and 2 play fine, but Timeline three gives me this wierd error, eventhough it’s using the same files. This morning i was able to do a mixdown so I can rescue my project and all is not lost. But does anyone know what this error actually means?