AN UPDATE:
Especially to Thierry, Dave, Doug, ... some further news.... I have
just had a note from the chap that supplies my bits'n'bobs
(BTW ...anybody know of a reliable UK wholesaler of medium quantities
for DRAM/Processors/hardware/etc?) ... he has spotted (must get myself
a new pair of specs or even learn to read... I looked on gigabytes site
but I misseed this) that Patriot modules (which is what we have used for
this) are not listed as being tested/approved by gigabyte. It could be
that they are drawing too much current and that would explain the
stuttering, and also why when Thierry upped the power it worked. (You
might not have used Patriot chips Thierry...but it could be that they
too were out of recommended bounds for power needs.)
I'm going to get the Patriot units swapped for 4 'listed' modules and
see what happens then.... will update the list with the results... but
if this is the root then others may want to take note that the Gigabyte
board/set-up seems to be power-critical (sensitive) if all slots are
populated.