First thing is first, you're not removing any connectors or anything while it's on, are you? A BIG no, no!
That little board up top (The one not connected) is the reset board - useless in home use.
Did you try pressing the board on the mpu in? It's the one you removed the game rom from. Did you reseat the rom back in right? I see you got the flashing light on the sound board which is a good thing. Try to reseat the connectors again.
If all else fails, you must do the ground mods.... some bizarre things happen when these boards don't share the same ground w/ the cabinet - like your instance...