"Could Not Save All Data And Formatting"

[David Benson]

I have a fairly large spreadsheet (~20,000 rows, 26.8M file size). Most of
the occupied cells contain VLOOKUP formulas that reference different
workbook. When I close this workbook, I get the message "Excel could not
save all the data and formatting you recently added to FILENAME.xls", where
"FILENAME.xls" is the file name of the workbook in question. If I select
the option "Continue saving changes without repairing the problem", the
spreadsheet appears to save OK. If I close the spreadsheet and later
re-open it, I cannot identify any problems or lost data or formatting.

Does anyone have any idea what causes this message, and what I am loosing?

Thanks,

-- David