Here's a save that reliably reproduces Nemesis Fail error.

There's a dwarven fortress Holycrypts I created some time ago. Now I retired it. I wanted to create a dwarven adventurer and Holycrypts was the only fortress available.
The game crashes whenever I try to create a dwarven adventurer, and everytime I try to enter the site as other race (human) adventurer, so I guess the game cannot load the site.

The fortress was created in 40.09.