After quite a long gap I have finally got around to changing from the nVidia drivers to the vesa ones. I did try to use the Nouveau ones but they were excluded by default and when I allowed the kernel module to be loaded my system froze at boot just as the warning comment said.
(From my Xorg.0.log) (II) LoadModule: "vesa" (II) Loading /usr/lib/xorg/modules/drivers/vesa_drv.so (II) Module vesa: vendor="X.Org Foundation" compiled for 1.7.7, module version = 2.3.0 Module class: X.Org Video Driver ABI class: X.Org Video Driver, version 6.0 (II) VESA: driver for VESA chipsets: vesa I will try to enable the 2nd monitor as I had done previously and I will update this bug if I see the original problem again. Tom - BlueArc Corporation<http://www.bluearc.com/>, now part of Hitachi Data Systems<https://www.hds.com/>