OK, Microsoft. What the hell?

A random Exchange 2010 service, in this case the Microsoft Exchange Address Book (MSExchangeAB), simply failed to start after a reboot. No errors in any logs, it just timed out. No troubleshooting information anywhere online. I thought about it a little and popped open the microsoft.exchange.addressbook.service.exe.config file and what did I find? This at the end:

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This is the exact same issue that has happened with another client’s Hyper-V Server, though there, an XML configuration file belonging to a Hyper-V VM is the being corrupted and disappearing from the Hyper-V console as a result. It happened to them twice and we were never able to find out why. I doubt I’ll ever find out why this just happened but I sure wish I could get the last two hours of my life back.