23" Cinema Diplay Flash/Flicker

My mother's Apple Cinema HD Display 23" (M9178LL/A) bought in 2006 is giving her two types of intermittent problems, namely, (1) Flashing/flickering, and (2) Spontaneously drawing squares as if she were using her mouse to select an area.

She took it to an Apple Store and of course she was not able to reproduce the problem. The Genius told her that the display is too old for Apple to do any diagnostics or repair.

She uses the display with a mini-DVI/DVI adapter (M9321G/B) connected to a 13" Intel MacBook running OSX 10.6.8.

Can anyone speculate on the cause of the problems with the display?

Thank you for your attention.

- nello