Hi, this thread caught my eye, as I had similar problem, yesterday, while doing the new Heroics, on random dungeon finder. I tried in-game reset, as well, but no change. Finally had to log off, then back on, and player frames were back. However, once we started playing again, I lost player frames, and the box showing buffs, on the left side, above the chat box.
I have not had any problems with NUI+, until now. Fortunately, I was in my Shadow Priest spec, instead of my Disc...would have seriously screwed up my healing!
The only thing different I can think of, is that I've been changing the nui framerate, to see what happens. I had set it to 35, as I have a new I7 computer, with lots of power for gaming.
The problem also went away, as soon as I zoned out of Halls of Reflection...
Mr. Spiel, I don't consider this a big deal, at all, just wanted to FYI ya...I tried a lot of add-ons, in the effort to get my UI clean and functional, but yours has been the best I've had, by far...(two thumbs up, and Happy Holidays!!)