problems with QT settings for DV capture

Hi,
I hope to find some help from your part because I'm stuck with a dvcam capture problem.
My FCP capture settings are DV PAL 48 khz (I'm in France) and when I open the capture window, I get this message:
'an error occured during the QuickTime settings for the capture parameters. Quit FCP and check your hardware configuration'

the deck controls are OK but I have of course no preview.

I've changed the firewire cable, downgraded QT to 7.6.4 (with Pacifiste), removed the FCP and QT preferencies.
No effect. The problem remains the same.
Nevertheless I think I've done this in the past with success.

MacPro OS 10.5.8
FCP 7.0.3
deck SONY DSR 20P (miniDV and DVCAM)

Could you help me ? I would be very gratefull
Regards

Philippe Muller