Plot area changed after reopen document
 

Hy,
I have problem with unstable format 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?
Thank you for help.