After the last cooker update I found through update-alternatives that
the opengl interface was not using the nvidia opengl drivers. I have
used update-alternatives to set the opengl drivers back to nvidias. I
also found that xorg.conf had the video driver set to nv instead of
nvidia, which I have now changed back. Why is this occurring as this is
not the first time this has occurred, particularly when the video driver
version has not changed during the update?

regards,
Steve