No boot after Natty update

On Wednesday (14/07/2011), I was alerted to an impending update on Ubuntu 11.04 on my Dell E520.
This was quite a large update and included a new kernel image (2.6.38.10-generic) to replace the existing 2.6.38.8-generic.
Well, the update went fine, but when I rebooted to the new kernel, the resulting Desktop froze. The clock was stopped and it was impossible open any apps. Nevertheless, the mouse and keyboard still worked.
I tried rebooting a number of times, but always got, more or less, the same thing (although now and again, nothing at all appeared in the upper gnome-panel).
I also tried booting to both the 2.6.38.7 and 2.6.38.8 kernels but neither booted even as far as a frozen Desktop.
I always remove the "recovery" options from the Grub2 menu, but I did try adding the word "single" to the linux kernel line in the stanza for booting the 2.6.38.10 kernel, however, this gave an error and didn't boot.
Nevertheless, when I booted back to the 2.6.38.10 kernel, even though the Desktop was frozen, by pressing Ctrl-Alt-F2, I got to a tty.
Now after logging in, using "sudo su" to get a root prompt, I ran "update-grub" in order to add the recovery boot option to the boot menu.
A reboot enabled me to boot to the recovery options menu. From this I initially tried the "dpkg" option to repair broken packages. However, even though this seemed to go OK, it still didn't allow me to boot to a normal Desktop.
Back to the recovery options and this time I chose the Failsafe Graphics option.
This booted up fine with everything working including Conky and wobbly windows. The only problem being the reduced screen resolution of 640x480.
Nevertheless, this strongly indicated a video driver error as well as giving me the opportunity to download the nVidia 173.14.30 driver that had worked fine for me before.
Additionally, I had posted before about this driver being easily broken in Natty on updating.
Anyway, with the driver downloaded to the Desktop, I used Ctrl-Alt-F2 to get to a tty and thereafter (as root), cd'ed to /home/paul/Desktop and issued these commands

# service gdm stop
# sh NVIDIA-Linux-x86-173.14.30-pkg1.run

This went smoothly and on reboot, everything on the Desktop was back to normal.
However, I don't have the impression that the update, on this ocassion, actually broke anything. Rather the problem was that the nVidia driver wasn't compiled for the new kernel.
But, this doesn't explain why I couldn't boot with the 2.6.38.8 kernel either and this is the one that the old driver was compiled with.
Strange, but at least it was easy to recover from.