I am running into an interesting problem, I have never ran into before. I am exporting a quicktime movie all setting exactly the same, but notice that the output movie seems much hotter then the timeline footage.
What is your operating system? Is it playing back the QT under the same ColorSync rules as Final Cut is using for its display preview? Have you brought the exported QT back into FCP to check its video parameters?
"I always pass on free advice -- its never of any use to me" Oscar Wilde.