I think I saw this problem earlier on the forum.
Set profile to High and try again.
That was indeed the solution, thanks! But why could it suddenly be a problem after an update?
When creating files for computer/online playback (not editing), then best practice is to simply use square pixels with 1.0 Pixel Aspect Ratio, which will ensure that ALL players correctly display your video, no chance of problems.
Export as 1024x576 with 1.0 PAR and that is the square-pixel equivalent of PAL DV widescreen.
For NTSC users, I've seen it two ways, either 864x480 or 854x480.