As part of the switch to Visual Studio 2012 I had also updated the program version number in the .rc file using a home-made program that processed all of my AssemblyInfo.cs and .rc files, and it had changed the encoding of the .rc file from ANSI to UTF-8. And the Microsoft Resource Compiler can't read UTF-8 files properly! http://social.msdn.microsoft.com/Forums/hu-HU/vcgeneral/thread/e212069d-678e-4ac8-957f-7d60d3e1c89f
So the solution is to re-encode the .rc file as ANSI or UTF-16.