Decklink HD Extreme causing sluggish playback...

Hi:

When I switch to view sequences on my external monitor and hit the space bar to either play or stop I get an annoying delay. If I switch back the External Video to Off the delay is gone. The ALL FRAMES in External Video seems to cause the problem. When EXT VIDEO is swithched to OFF FCP is really snappy.

I use 10Bit uncompressed Pal Material. My settings in FCP for External Video to view in SDI are EXT VIDEO: ALL FRAMES, VIDEO PLAYBACK: 10BIT UNCOMPRESSED PAL with AUDIO PLAYBACK set to AUDIO FOLLOWS VIDEO.

Can anyone help.

Thanks

Eddy.

Quad, 4.5GB Ram, Decklink HD Extreme, Ext SATA RAID 1.5TB, JVC TM-H150 with SDI card, OS 10.4.8, FCP 5.1.2, Blackmagic Driver 4.8

Correction Decklink driver should be 5.8 and not 4.8. I recently switched from 5.7.2 to 5.8 to see if this made a difference. It did not except for a strange looking SPEECH Icon in system preferences so I have switched back to 5.7.2. Anyone have any ideas