I found a fix for the crash after hitting the play button, at least for me. Open Steam. Click on the Games tab at the top of the screen and click on 'View Games Library' on the drop down menu. This will give you a list of all your Steam games. Now, right click on 'Fallout New Vegas' and another menu comes up. Click on the properties tab. This will bring up another menu. On the lower half of this menu is a box marked 'Enable Steam Community In-Game'. Un-tick this box. Now the game MAY run normally. At least it did for me. I have been playing for about 10 hours with several mods enabled and I have had only one CTD the entire time and i think this may have been caused by a different program I had running in the background. I certainly hope this helps everyone.

Didn't work for me.