Our engine has been modified to log for us when it stalls for more than 30 seconds and continue regardless of if the event is called or not, you will see the point when this happens in the log, rest assured that this is the moment when the game would have otherwise frozen forever. link text
We are trying to reproduce this in a fresh project currently, while trying to hunt down what could have caused it in the first place. This is very difficult and time consuming, but we will let you know if and when we find a good repro case.
We can reproduce this offline.
We have tried disabling and enabling all of these features, the results are the same.
We have been able to reproduce this error on our current project with all of our async code removed, we are working now to determine if the assets that were async loaded may somehow be tied to the error.