I've encountered the very same problem.
Tried everything mentioned, tried holding "P" and clicking on the Halo icon to bypas the processor thingy. Nothing works.
When I click on the Halo icon, installed into my home on an administrator account it opens the settings window. As I have for the past few months, with the same settings and hardware, I click on "OK." The Halo title image loads, flickers, and after about 2 seconds the program crashes. I've sent the report to Apple, and searched the web - has no one found out how to get Halo working again?