Final update, after a very productive exchange via the redhat bug tracking system, it turned out my BIOS was causing the problem. Flashed the latest version an d voila it works like a charm. (Samsung Q45 BIOS ST7 to version ST11) Before that I could get it to boot with kernel options pci=nomsi acpi= off before the crashkernel and rhgb quiet removed. Maybe someone will find this useful in the future and won't have to feel as stupid as I do at the moment for not catching something as easy as this. regards, Matt