Have you tried checking the Steam Cache, same thing happened to me after the 1st patch, right click the game in your steam list, left click properties, Local Files tab, click Verify Integrity of Game Cache - after about 10-20 minutes it should fix any bad files and send you back into the wastes without issue.
Yeah Checked that said some files where invalid, re downloaded them had another crash checked again had another invalid file. which made me WTF a little. If it continues I'll reinstall