Chart disappears in Excel 2000
 

I have a VB6 application that creates reports in Excel using Excel
templates. I retrieve data from a SQL Server database, populate certain
ranges in the Excel workbook which, in turn, supplies the data for the
chart. This all works fine. Infrequently, when a user creates a report,
the chart(s) will disappear when they close and reopen the file and I
have been told that this may happen when the user is clicking on
different tabs in the Excel workbook. I know this sounds bizarre, but I
have seen it happen with my own eyes and I am totally perplexed. The
Excel version is 2000 and the O/S is Windows 2000.