Have been trying to troubleshoot this exact problem for a bit now and found this thread as I am looking at trying out Kodi.
I have got it successfully booting by replacing the firmware files with those suggested.
I also tried doing a fresh image and then updating config.txt with the following: core_freq=250 which the OP said allowed it to boot, however it then wouldn't boot for me. I'm not sure if I put the line in the wrong spot or if it requires any special spacing.
With the replaced firmware files at least I can now boot and setup Kodi.
