Ok so I read countless threads about how to fix the game crashes and nothing worked for me.

I had the Unable to connect, I had Load->immediate crash and I think 2 more.

I already had a FNV game but bought Ultimate recently because it was cheaper than all the addons combined. I uninstalled the original game and installed only the ultimate. Then I noticed that even though I had only one game installed, I had 2 FNV folders under my steamapps: One FNV and one FNV enczplru - This second one had all the relevant info and the Launcher from this folder was causing the Load->crash issue, while the FNV other folder's launcher said steamapi_dll missing or something.

So I copied everything from the enczplru folder to the FNV folder. Tried the launcher from this folder and voila, game started!

Maybe it will fix your issues as well.

Good luck