Pivot Table Headaches!

When I try to edit my pivot table ( add a new row) - I keep getting a message that says "Microsoft Excel cannot make this change because there are too many row or column items....."

My original database is relatively modest - 1000 rows by 12 columns, I am trying to create a pivot table with 1 page field, 5 rows, and one data element. - but it won't let me.

I had thought that the maximum number of rows or columns was only limited by available memory - & I am running with 128M of RAM - does anyone else have any ideas?????

Thanks