I had to reboot it twice (via the power button). The second time it came back up fine. Its running as a virtual machine (under Esxi 5.1) and I did notice something odd. If I look at the performance graph over the last two hours (before I rebooted it), you can see the processor is pegged in that session to 100% however right now, its barely even registering.
Also, in the for what its worth department, this is the same machine that I've filed bug reports on in the past. Every once in a while, it will stop serving proxy requests from clients. I have to go to the proxy filter setup and change it from permissive to disabled (or disabled to permissive) and then save the configuration. Once its saved, the proxy requests start working again. When it died this morning, it was in the middle of a user using a browser.