For those of you using Mac OS X, there is a bug in the Socket implementation such that the broadcast socket option is not set by default. This means that it is not possible to broadcast from the current VM in OS X. The Mac OS X VM team said that this bug has already been fixed, so it's just a matter of release dates at this point. In the meantime, you should be able to work around this problem by specifiying the IP on the commandline.