Sorry for the long gap between posts but now it's working I thought I should post an update. After working through with support they gave me instructions to reflash the BIOS. I'd taken the second controller out and had it sitting on my desk for a couple of weeks and when I put it in, it booted straight past the error. So, same suggestion that Peter made but instead of 10 secs, I waited 2-3 weeks. I then reflashed the BIOS and all has been fine since.