Greyed out "HIGH" Quality in RT, anyone?

Been working through a weird issue I've been experiencing when playing video through an AJA IoHD. AJA recommends setting Video Playback Quality to HIGH in the Prefs, but when I create a 1080i 29.97 ProRes HQ timeline the HIGH setting is greyed out (under the RT dropdown). It defaults to MEDIUM no matter what the preferences say, and that led to several kernel panics when I had a mixed format timeline and was trying to play it all back at 1080i. Setting RT to DYNAMIC playback works fine, and turning off the video output through the IoHD returns the HIGH setting. I'm using a G-SPEEDes RAID for playback, which should be able to handle the ProRes.

I found an old thread on CreativeCow where some Kona users experienced the same thing with ProResHQ footage, but they never resolved it. Has anyone here seen this before? AJA support has been patient and helpful but they're not sure what's going on either. It's been suggested this might be a RAM issue...

JK

MacPro 2.66, 6GB, 10.5.3, QT 7.4.5, 3TB G-SPEED RAID, IoHD v5.1.2

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SCQT! Self-contained QuickTime ? pass it on!