The problem was a loose board slotted into the main board. After pushing this board in with my hand the problem was corrected. Works perfectly again. PS Audio told me to do this and their customer service was great (very prompt emails).
PS Audio UPC-200 problem.
My PS Audio UPC-200 has developed a strange problem. The power keeps shutting down, but if I turn the UPC-200 upside down or on its side the power will come back on and stay on providing that I leave the UPC-200 on its side or upside down. As soon as I turn the UPC 'upright' again the power cuts out. Is this a 'short circuit' problem and does anybody know how to fix this problem? Thanks.