Based on the description of the problems you mentioned and checking the system configuration (components used), I there is something than can be causing the problem.
For the DH77EB & DH77DF motherboards, the minimum recommended power supply is 460 W. I noticed you typed 120W. This may be the reason why the motherboard freezes and it is not booting when having the Card connected.
You can check the power supply considerations for both motherboards by accessing at the following links:
DH77EB on page 60:
DH77DF on page 64: