I'm not going to call it a bug, but it does seem to be an 'issue' with 2007.
I had a similar experience. We pulled in some data to be x-y scatter
charted: 51 graphs with 8800 data points each. Excel 2007 takes around 12
minutes to process and graph the data, Excel 2003 takes under 2 minutes (on a
slower machine even). I had a couple of other issues with graphing in 2007
and put them all into a pile, wrote it all up and passed it on to Microsoft.
I believe my package has been escalated up the line to the charting group for
Excel in-house, but of course I haven't gotten any feedback on any of that at
this time.

I do know that the charting engine was rewritten for 2007, so it's not the
same engine that was used in previous versions.

And yes, once the charts were created in 2007, Excel's responsiveness
dropped to a snail's pace - click a cell and wait one or two seconds for
Excel to acknowledge the selection change. Other programs running were not
affected. Machines used to try to deal with this were an AMD X2 4800+ based
system with 2GB RAM and an Intel E6600 based system, again with 2GB RAM; both
with Windows XP Pro.

"jojobold" wrote:

Dear all,
I have a problem with Excel 2007. I imported a lot of datapoints, lets say
250.000, and plotted those in nice x,y scatter plots. Unfortunately excel
slows down incredibly, and consumes more than 300MB RAM (and rising). Is this
some bug? (note: installed office 2007 couple of weeks ago on my <1y laptop,
1GB RAM, Centrino, plenty of disk space). Any way to fix it?
Best,
Joris