Hello,
I have just downloaded the Beta 1.5.6-r2 and cleared off previous issues in Win8.1 install. However, following the instruction for Automatic installation of Libraries I come to a halt. Arduino would still reject Library name spelled like "Marlin-Marlin_v1". "The Library cannot be used" due to name...
Try replacing the dash in Marlin-Marlin with an underscore (Marlin_Marlin).