The "GenerateResource" task failed unexpectedly.
System.TypeInitializationException: The type initializer for 'Microsoft.Build.Utilities.FileTracker' threw an exception. ---> System.NullReferenceException: Object reference not set to an instance of an object.
I dug around and found numerous references to existing bug reports and a few workarounds. I tried unsetting the readonly file system attribute in my solution folder, setting the GenerateResourceNeverLockTypeAssemblies property in my project file to true or false to downgrade some security parameters, but ultimately it was the top answer here that did the trick.
I had set the environment variables for the RAM drive initially to just R:\, referencing the root of the drive. Apparently VS 2010 doesn't like this, so I simply created a new folder on my ram disk named TEMP, and then updated the environment variables accordingly:
Just to rule it out, and also because I hadn't rebooted Windows in a while, I also opened Control Panel => Programs and Features, and performed a Repair on Microsoft .NET Framework 4 Client Profile just in case the framework files might've gotten corrupted somehow, and then restarted.
Problem solved! Now on to see whether Joseph Fluckiger's experimentation which returned lukewarm results on performance of building to a RAM disk holds water for a solution with, say, dozens of projects.