I have tried this at least 10 times. Every time I install the override chip in the control room at the dam, and I make my choice with Yes Man (send power to Fort), as soon as he finishes telling me that I have to flip the switch then go up top and deal with Legion and the NCR, the game crashes. Always in exactly the same spot.

I have been persuing the independant NV route. I only have 1 follower with me, Willow, and the MKII securitron that won't leave. Any other companions I dismissed and told to go back to the Lucky 38. On one of my tries, for whatever reason, Arcade appeared and offered the Enclaves help, which I refused. I have the FONV Ultimate Steam version, fully up-to-date.