Excel 2007 crashes continuously

Brand new computer, pre-installed Vista Business and Office 2007. I handle large workbooks - 50,000 to 500,000 rows. Excel crashes every time I try to insert a column or delete more than a few thousand rows. Spreadsheets are simple - no formulas, its data only. Sometimes it crashes simply when I "select" a large number of cells.

Interestingly, it can handle large volumes of complicated lookup formulas and pivot tables with little problem.

I have operated for a year with Excel 2007 on XP, and had a number of crashes, but nothing like this.

I have re-installed Office 2007, along with SP 1.

Any thoughts?
Thanks