Just an update: I checked the bios that gave me black screen: It has a core frequency of 1200 and memory frequency of 1700 (that's 3400 MHz effective!!) on a vcore of 0.974!!!!

So the flash was technically successful, only the poor bastard was freezing on the spot due to high clocks and low voltage!

Take home lesson: Open up your file again before flashing and make sure everything is the way you intended it to be.