One quick question/thought...
I notice your using the same BPPC as me. When you try to boot into OS4.0 how far do you get ie: it should be red screen, blue screen & purple screen = successful boot into OS4.0
If your only getting as far as the blue screen then your forgetting to (if you have it enabled on your BPPC) disable the ReMap ROM feature as OS4.0 wont work with this enabled...
Either hold down the two mouse buttons from power up to enter the early startup screen and boot OS4.0 from the partition it's on, or if like me you have a reset button on your Amiga hold it in for ten seconds and this will switch off the BPPCs MapROM feature...
As I say OS4.0 will not work (you wont get past the blue screen) when the MapROM feature is active and the kickstart has been re-mapped (same applies if your using BlizzKick to ReMap the ROM)...
I reach the purple screen that goes on repeating...
Anyway I checked in the BPPC BIOS and the MapROM is disabled.
Another user told me that he had the same problem as mine and he had to remove the IDEFIx... but I do not want to!
since other users do use it and if Hyperion writes that it works, it SHOULD!!! But I have not been able to...
After reaching the purple screen I also tried to reset with C+A+A, with the button on the case (yes, I made the mod)... nothing.
Do you have a 603 or a 603+?