So, I can't finish dialogue with Elder McNamara after entering the bunker. Tried using different choices and different saves, but ultimately the game crashes.

Are you using mods?

Have you tried a game cache verify?

game cache:
1) Open Steam
2) Right click on Fallout: New Vegas
3) Hit Properties
4) Click the "Local Files" tab
5) Click on "Verify Integrity of Game Cache"

I am using CASM and have NVSE istalled. Verifying game cache didn't work.

Issue resolved, thank you.