Having a similar problem. Seems to be a glitch in FCP, because it is now happening on a regular basis. Images look fine in FCP, but on export there is a weird banding effect. Sometimes the image is completely gone, revealing the layer underneath. Occurs whether viewed on computer or video monitor. Occurs after deleting render folder and re-rendering. Project due tomorrow, am now at wits end. About to reinstall FCP…
FCP 6.0.5
Unibody Macbook Pro