I had the same thing happen, but slightly different from what I've read here.
I played a good 4 hours yesterday after work and had a great time (awesome game!)
After learning a thing or two, I decided to start over witha new region. After about 5-10 mins, the game crashed, exactly as you all have described. I started the city a good 5 times and it did finally save, from then on I could play. However, a major bug started: The graphics were all buggy. First off, the main menu screen was weird, The image of a city just wasn't there, a sillouette and blue sky replaced it (as well as a faint image of my saved city in the backgound (wtf?). Entering a city didn't prove to be any better, there were no road guides and when I tryed ti place a road, the "ghost" image of the road was a muddy brown color. In addition, I couldn't see the city limits and water was not rendered. Instead I just see canyons where a river should be, with boats hovering over it.
I'm reinstalling the game as I write this, I'm sure this will solve nothing. Hope they fix it soon because this game is crack.
edit: Specs
i7 2600k 3.8ghz
8g ram
ati hd 6950