Maybe the lastcell in the worksheets is way past what you think it should be.
(although that's one big leap).
If you hit ctrl-end, you go to the bottom left corner of the used range.
If that's way past what you think it should be, you can visit Debra Dalgleish's
site to see some ways to try to reset that lastused cell.
http://www.contextures.com/xlfaqApp.html#Unused
I don't use shared workbooks (or track changes) enough (ever!) to offer any real
help.
Sorry.