The green flashing light you referred to is described in Para. 1.11.2.10 of your Technical Product Spec found here: http://downloadmirror.intel.com/22679/eng/DH87RL_TechProdSpec03.pdf
I could not boot into Setup with a DH87MC board using HDMI and found out I could get into the BIOS using DVI and was then able to load the O/S. Regards. Peter