I realised my last post might be a little misleading. My system boot is not error free. I still get the "disabling IRQ" problem on some boots. I'm using GRUB and the trick appears to be to allow a considerable dealy before initiating the boot, but it can be a bit hit and miss.

I went back to the Knoopix 3.8.1 CD and played around with expert mode and other combinations with various lengths of delay before hitting the enter key on the initial command line. Out of a dozen or more attempts I got the system to boot correctly just once! So apart from this irrating bug which prevents the system from being usable, there were no other obvious problems.

Has the kernel update in 3.8.2 fixed this SATA/Kernel bug? If anybody has had success with 3.8.2 on the same/similar hardware to myself I be interested to know.