Someone at EA said they fixed almost every problem.

Check the number of "flames" in their forum, countless... and all currently getting filled with new lost cities every hour...

http://answers.ea.com/t5/Miscellaneous-Issues/bd-p/sim-city-misc-issues

I'm really shocked. I lost my city as well, and not only one.

They should gift us Sim City 2014 and not another game we don't care of...

I'm not sure, I had the same issue more times, then I figured out it was just a matter of having people in the city and the ones I had were not enough, despite the industries' message was not very clear.

Also, this happens when you put high density roads around the industrial areas. So when you do that, do slowly or make the city be crowded first.

To do that, just lower the private's (citizens only) taxes to 7% or less, they'll come in and will let your city double, so your industry will keep up (that you then must tax for about 10% or you'll not be able to earn money).