You are using Visual Studio 2012, where you are editing a Visual C++ project and making changes to a dialog in the Resource Editor. An unexpected message box appears with the error message:
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There is an issue with how the AutoRecover feature is interacting with the Resource Editor. When the resource being edited has not been saved when the AutoRecover interval expires (the default is every 5 minutes), AutoRecover tries to save the resource files. During this, it tries to save a file named resource.hm. Resource.hm is used when you are using Context-Sensitive Help, an option when generating a native UI project. When you have it enabled, it creates help IDs that get written to the help ID header file, resource.hm. There will not be any resource.hm unless you enable the "Help ID" property for one or more of your resources.
See this blog article about AutoRecover: Ultimate Visual Studio Tips & Tricks
for other considerations.