http://www.pcgamer.com/fallout-4s-first ... een-found/
What is apparently the first "game-breaking bug" in Fallout 4 has been reported on the Bethesda forums. According to user JoeBBBB and several other posters, traveling to Monsignor Plaza can cause a crash to desktop, with no error message reported.
The initial complaint, which actually goes into quite a bit of depth about how it all works, says the problem appears to come up once players have passed a certain point in the game (the post goes to lengths to avoid spoilers, as do I), or after they've unlocked/passed a certain location. The problem is compounded by the fact that Monsignor Plaza is a location in a settlement quest, and once that quest is accepted, you're stuck with it.