As far as I know we have the correct codec. This is the first time that this has happened. It did not happen in CS4.
When I select it in the project window it has this info: 1920×1080 (1.00), [time info], Millions of Colors, MPEG, 48.000 kHz / 16 bit U / Stereo
The clip works perfectly in Final Cut Pro.
Thanks for your very quick response!