A solution in case someone else runs into this problem (or if I do in the future after forgetting about it), and because I spent a lot of time looking on Google, with solutions that didn't help:
the context:
- new installation of Fallout New Vegas, on a machine where it worked a long time ago
- windows 7 pro 64-bit
- i7, 8GB RAM
- Nvidia GeForce GTX 285
the problem:
- can't start the game, there is the movie, then a loading screen and it stops with the message "Fallout NV has stopped working"
the solution:
- install new drivers for the GTX 285
- the trick is that NVIDIA GeForce Experience was telling me I already had the last drivers
- going on the NVIDIA website and comparing the version numbers showed me there actually was a new one
- might have helped: I did the advanced installation and checked "clear profiles"; changes I made for other games could have screwed it up
- there was no need for compatibility mode, or any other of the dozen of tricks found on google