In reply to:
The flyback transformer is the culprit.
Further to this, there are also some inductors on the main board with ferrite cores encapsulated in plastic. The ferrite core develops a chip and the voltage running through the coil causes the ferrite chip to vibrate within the plastic casing at a high frequency. This frequency can vary from set to set (when it fails) and is extremely annoying. It usually occurs at a frequency lower than that of the flyback and is more audible (drives me nuts).
