I'm having the same problem as Screenstory, running a similar system (late 2013 Mac Pro) and Premiere Pro CC 12.1.2 build 69.
I also don't understand what is meant by "...opening the sequence first with another video." I've tried creating a sequence by right clicking on a video clip in the project panel and selecting New Sequence From Clip. Same result.
Any advice from Tech Support? Please?