Update.
It looks like it does not work in Full HD either. When I render at 60 FPS, I get 15-second videos that play correctly under Windows built in player but every other program sees them as 15-second videos. When I render Full HD at 30 frames, my video shows as 30-sec-long. I've tried now with 1.7.1 and the result is the same.
I used to be able to export animations as videos in Full HD.
I keep trying with a 2-minute long animation and each time the result is different, but it does depend on resolution and framerate. It shows as 1- to 30- sec long, but the actual content of each file when played underwindows is always 2 min, as it should and the stream looks good. But since only this one player sees the actual length of the stream, I cannot work with the video or convert it.
When played under VLC Player, it shows some kind of index error and goes into a loop of fixing it. All I see is progress bar there and once it gets to 100%, it restarts the process, so I never actually see the video there.