I have 12.04.1 installed on my laptop - it's a Lenovo E530. I have a small /boot partition on the internal drive, with /, /home and swap on an external hard drive, which is USB 3.0. I used it for quite a few weeks without any problem.

Yesterday I updated it, which I forgot to do for some time, using the Update Manager. There also was a new kernel version. It seemed to have gone OK, but after rebooting the system just froze: black screen, no response from the keyboard, no sound from the hard drives, completely wedged. I had to switch the machine off.

After restarting again, the system wanted to check the disks. Fine for me, but the problem nw is that it gets stuck in a loop: after checking the first of its list (I don't know which one it specifically is, it just says "Disk 1 of 4") I hear a faint click from the external drive, and the system resets. Then it repeats it all again.

If I skip the checks, after the Ubuntu screen with the dots on a black background, it goes into a black screen again. No response from the keyboard, again, but this time I can restart with Control-Alt-Delete.

The computer boots normally into Windows.

It was really odd that this happened after an update. Is it usually better not to have a big bunch of updates in one go?

More data is probably necessary to diagnose this issue remotely, so any suggestion on what to put here for further information will be appreciated.

Just a suggstion. Since the pc is having issues with checking disks you do it manually. Just use a live linux medium and run fsck on the hrd drive.
Apart from this - installing updates when it comes to Ubuntu is something I would not prefer. Next time try and install only the security updates. But I would not be qualified to answer that question as I have used Ubuntu ages ago.

Hope this helps