Success! As I was reading up on unRAID NAS at their website they recommended plugging the USB key directly into the mobo and not using a front port which I was for convenience.
I plugged the key into the back of the PC and in BIOS changed the "Hard-Disk Drive Sequence" to "Option 1. USB Device" and now it boots like a charm. (After flashing the BIOS to A12 as per Speedstep's post)
I had tried this before but with the USB key plugged into the front port it didn't work unless I booted as I outlined in my previous posts.
