Perhaps I'm missing something here...

require 'ffi'

module Hello
  extend FFI::Library
  ffi_lib 'user32'
  attach_function 'FindWindow', [ :string, :string], :pointer # blows
up
end

ref: http://msdn.microsoft.com/en-us/library/ms633499(VS.85).aspx

What might it be...?
-r