Just guesses...

The last used cell on each worksheet is way past where you think it should be.
See Debra Dalgleish's site to reset this last used cell.

http://www.contextures.com/xlfaqApp.html#Unused

Any chance you have objects (pictures/buttons/textboxes) in your workbook?

Sometimes pictures get duplicated by error.

Mark wrote:

I have a workbook that has recently increased from 5meg to 30 meg. There are
no pivot tables -- only a couple small macros that involve a few lines of
vba. What could have caused the jumped.. and what can I do to fix it?

--

Dave Peterson