Underflow simply tells the user that not enough data is being sent for AUNetReceive to process. Almost always, if you see this, the issue lies beyond Spectre.
Be sure you disable any applications or utilities that may interfere with your network.
If you're on a network (wireless or otherwise), completey disconnect your machine from the network and see if the issue persists.
Users have had success after removing their System Configuration folder:
Note: This is your System Library, not your User Library.