Well, I've just managed to fix my Mk2a. I've had the 'Contact Support' screen more than a few times over the last few months, now that the colder weather is here. Normally when I forgot to bring my Empeg in from the car and booted it from cold 1st thing in the morning.
Tried a new cable and a new drive to no avail, finally got round to having a look at the IDE header and could see a slight imperfection in one or two of the solder joints. Heated them up, flowed a little more solder on to the worst (and just heated the other) and 'Bing!' fixed.
I reckon it's fixed, cos every other time I've taken it to bits it has coughed up that error for about 20 mins of solid cable manipulation, swearing, physical abuse and weeping in the corner until finally starting to boot again. This time it fired straight up and hasn't put a foot wrong since </relief>
My new solder joint may not be the tidiest in the world, but it works