Monitoring HD

I want to monitor the output of my Blackmagic Decklink Multibridge when editing in HD, but the picture sent to the monitor when the timeline is played is frozen. When I pause the timeline, it freezes the current frame. The timeline is 720p, Pro-Res. This occurs on the composite and DVI output of the bridge. When playing an NTSC 8 or 10-bit timeline, playback is fine. This on a G-5, OS 10.4.1, FCP 6.0.6 and Decklink 7.1. I am able to monitor through the Panasonic HD1200A, which receives an SDI signal from the bridge.

Thanks!