I have a nether crash, also. I use Windows 10 edition to host for kids to connect from ipad/iphone devices. Host PC started crashing, and it appeared to be caused by anyone entering the Nether.
So I went into the Nether. Now PC host account is stuck in the Nether, and the game instantly cashes. Map is completely unusable until I can somehow fix whatever is broken about the nether.
Here is an exported .mcworld file for anyone to attempt to walk into the Nether.
On my windows 10 edition PC version 1.2.5 I am now able to load and play in the world that I linked above that was instantly crashing before.