On Mon, 11 Jan 2010 15:23:35 GMT, "Brian Gaff"
wrote:

Already done the ground thing, indeed, I have too good an earth and had to
be very careful with cable length to stop earth loop problems with
connected gear.

Well, the psu is not actually new, spare would have been a better term..
However it seems robust enough, but the fact the previous dead supply did
not have this does point to some of the switching artifacts getting into the
computer.

For ultimate low noise you could always swap the dead psu back in :-)