I think this represents a race condition:

I keep stock prices in vertical columns, the columns
being Date, open, high, low, closing prices, and sixth 
and seventh columns which are calculated from the fifth
column.  I then make three charts based on the fifth,
sixth, and seventh columns, respectively.

Typically there are several hundred rows, maybe >500, so
there are lots of calclations to do.

I place the charts near the bottom of the spreadsheet,
which seems to be the root of my problem.
 
I keep one constant stored in one fixed location also
near the bottom of the sheet, which I change from time
to time, and this re-calculates the entire sheet, and
redraws the charts as a result.

When I change the value of the contstant the charts go
blank.  I can force them to reappear by going through
a 'Modify data range' edit, even though I don't really
modify the data range--I just force a redraw which makes
the charts redraw correctly.

This seems to be a function of how many rows there are in
the spreadsheet--as I said there are typically 500 or so.
For much smaller sheets this does not seem to happen, which
makes me think of a race condition.  Also, if I place the
constant up near the top of the sheet instead of near the
bottom I can sometimes get the problem to go away, depending
on the number of rows in the spreadsheet.  Once again this
makes me think race condition.

This happens in Windows 2k, WinXP, and Linux also.

This is not a new bug, by the way--I'm just getting round
to reporting it now.

I like your program--thanks for the good work!