If you export a QuickTime movie from Final Cut Pro 5 in the H.264 format, it's possible for the operation to result in a message that says, "Codec error."
If this happens, no file is exported. This can occur if you choose File > Export > QuickTime movie, and then choose Custom, and set H.264 as the compressor.
To avoid this issue, you can export from Final Cut Pro via different export options:
You can export using Compressor, which offers a high degree of control over the options available when exporting as H.264.
You can also export using QuickTime Conversion, which offers fewer options than Compressor, but may be simpler to use.
This document will be updated as more information becomes available.