I have CS5.01 and am running the mercury playback engine using an Nvidia GTX285 with the latest firmware that came out today (19th July 2010).
I have a few clips I am slowing down and the frame blending is not being previewed using the mercury engine (using both time remapping and speed/duration). The timeline bar is yellow (for realtime mercury engine) and therfore does not render a preview.
Is this a bug?
As a work around I switch to software mode I can render a preview (which includes the blended frames) and then go back to the mercury engine electing to keep the previews.
Althougheven without a working, if I export the with the frame blending tab checked (they have added a default off tab for frame blending to the media endoder?) the blending does come through.