(Excel 2000)

I regularly add horizontal lines and text boxes to charts, using the Draw
tool.

When I return to the charts some time later I find that both the line and
the box have "slipped" lower down the chart. They can even end up below the
x-axis.

This happens all the time on some charts. but on others the line and text
box appear properly fixed. So far as I am aware I am not doing anything
different with them.

Is there a cure for this or is it a program defect? Any assistance
gratefully received.