I go into the portal, it spins and sometimes gets to the "building terrain" screen, but then the app shuts down. Tried making copies of the world, but no luck. I'm playing in single player survival mode. I had the same problem going into the nether, but after about 20 mins of reloading the app, I finally got past the building terrain screen. 

I've tried for about a day now, but still stuck in the nether.