Large spreadsheet - Charts don't refresh

[makrug]

I have a large workbook (40MB) and as it got bigger the charts stopped
refreshing automatically. Using Excel2003. I've tried forcing a recalculate
with F9. If I hack some of the data out to reduce the size it works again
(updates automatically). If I change the source data for an individual series
(not really changing it, I just delete a character and put it back again)
then that forces that series to appear on the chart, but since there are 255
series that approach is somewhat tedious.

Any ideas folks?

[makrug]

I am aware of the 255 series limitation, that's not the problem.