(I’ve edited this many times already… I keep discovering new things. Also, if this double posts, sorry about that.)
I just tried creating a new project and it rendered fine. However, when I tried to add the Timewarp effect like I did in my original project, and scrolled around in the timeline, I gor the error again. I tried experimenting with the speed of the Timewarp, and it seems that the higher I put the speed, the more often I get the error appearing when scrolling around. Below about 110 or so, I never get the error, but staring at 120, the error appears periodically, and at 500 it always appears.
I can think of no reason why this should be the case.
Also, I can’t imagine one of the images randomly being CMYK, because they are all from the same camera.
Any ideas are appreciated!