Thanks again, I tried this V1_RC bootloader and it seems on my limited test much more stable.
On a similar torture of my X-FI I managed 4 failed boots out of 20, with equal black and white screens. I'm more than happy to live with this
I'll report back in weeks time when I've given it some real world usage tests...
I may also look out for another X-FI just in case it's symptomatic of a latent hardware fault in mine!