Barbara,
I know this is my circumstances but I reinstalled the game (after getting the errors) and played unregistered until I was forced to register (because of upgrades). I then registered, noticed a delay between registering and being able to buy the upgrade but then went back into the game. I haven't had any problems with it since.

The only thing I can think of that was different was that after my reinstall I chose NOT to turn the tutorial on. I will reinstall VS and try this, if I can ever get it to crash again I'll try Arthur's method and report back.