@ICPUG post #8 and
@mecho post #9

My laptop has Intel GM45 video.
I've never noticed any video problems with Knoppix 6.2.1,
either at boot-up or otherwise.

However, recently I've been trying out a 2Gb SD Card version of Ubuntu.
Using the 64-bit Ubuntu version, the video was noticeably flickery.
The 32-bit version was less flickery, but still a little unsettling.

Adding the i915-kms.conf file to /etc/modprobe.d seems to have quieted down
the 32-bit version completely.

My thanks to you both for solving a problem I had no idea where to start going after.