So far this is what I think happens:
The game tries to load the family, fails, and throws an exception, then returns back to map view. It's always Willow Creek and not Oasis Springs that is loaded too.
From the files I've looked at, it always seems to have something to do with careers or school. I've forwarded this to EA but I do not know how fast they can/will react to the issue.
If tried two borked save games and I believe that if they have the issue, it will come back, even if you load a backup. Once I started a faulty game, I couldn't load mine either until I removed the auto save. It can even return if you reuse a family that already has a carrer/is in school. I think it should work if you completely start from scratch for the time being.
I'm adding a few more questions to the first post.
For those that say it didn't work, did you remove the files for now and see if you can start a new file ? The faulty save(s) and slot00000001.save need removing. You can save them to a save place and return to them once Maxis found the issue and was able to solve it.
This could take a while with Christmas Holidays around the corner.
I know many of your are upset at this but please do not blame the messanger. I'm trying to my best to make Maxis aware of this issue but there's nothing I can do about it. If anyone finds working workaround that does not involved ditching the save game, please let me know.