Usually, it just closes, and says "DB yada yada yada... has encountered an error. Would you like to send an info report to microsoft?", but it once said something about an array indexing error.
Also, internet mode never works.
In fact, worse than that, if I restart internet mode a few times to try to get it working, it makes DB crash with the aforementioned error.
However, I usually just get that crash after running a sim for about 1000 cycles.