I've set a default chart type in Excel, one that has my own preference
for line thicknesses, symbols, colors, fonts, etc. I'm basicly happy
with the time savings in not having to change these settings every time
I make a chart.

However ...

One small annoyance is that every couple of months, the default chart
type reverts back to the original default. Now, it's not all that big
a deal to reset the default back to the desired chart type I have
created. But what is bugging me is, why would this happen?

I'm fairly sure I'm doing something in Excel that causes the chart
default to revert. But, that something is done in a previous Excel
session (by the time I realize it has happened). So I am unable to
remember exactly what I could have done to cause the default to change.

Any ideas welcome.

Thanks,

Mark