It is a Dell flat screen monitor. Unfortunately, it is not that old. It just occurs to me that it may still be under warranty. I suffer from CRS syndrome, and off-hand don't remember if I bought this computer 1 or 2 summers ago. Guess I had better go digging for papers.
I was playing a DVD on the computer.
The problem is spreading, with the bars starting to appear further and further down the screen, and showing on the whole screen at start-up when it is all black except for the Dell logo. So it seems pretty clear that the monitor is going kaput.