Comment 1 for bug 322673

Since posting this question I have deactivated the NVIDIA driver that was recommended and now the computer boots without an error message.

In the course of all this, I tried all three NVIDIA drivers none of which worked. However the recommended driver had been working fine until the last couple of days. The problem seems to have coincided with the latest updates - I downloaded them either early this week or late last week - one of which had something to do with X11 (I think)