[Brian Dowtin]

I had the same problem – linking to motion from Final Cut.

The fix: after selecting ‘Variable Speed’ in the time remap window, (and the preview goes black) go in and select it again.

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To reproduce the problem : Export clip to Motion. In Motion – you’ll find the clip in a Group (Group 1) , Select the clip, go to Timing, and in the Time Remap field select -‘Variable Speed’; The preview for Group1 – turns to checkerboard, and the main preview window turns black.
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Hope it helps!
‘Brian