Chart Plot Area changes in Excel 2007
 

I having problems with unstable formats of charts in an Excel 2007
spreadsheet (under Windows XP). When I re-open a spreadsheet, the plot area
is usually contracted to a much smaller portion of the total chart area,
leaving lots of white space around the edges. This happens repeatedly with
some, but not all, of the charts in my spreadsheet. Some are x-y plots, some
are combination line, bar plots. Is there any way to keep the size of the
plot area from changing?