In some cases, rendered items may become unrendered after quitting and then re-opening a project in Final Cut Pro 6. In these cases, the render bar will indicate that the items are rendered, but if you attempt to play the video, you will see "Unrendered" in the Canvas.
This can happen if you duplicate a sequence with rendered items, then quit, then re-open Final Cut Pro. The duplicated sequence will remain rendered, but the original sequence may require re-rendering.
This issue has been resolved in Final Cut Pro 6.0.2. Final Cut Studio 2 users can update to Final Cut Pro 6.0.2 by choosing Software Update from the Apple menu.
Notice: Pro Applications Update 2007-02 needs to be installed first. Afterwards, you will see updates for Final Cut Studio 2 applications in Software Update.