Automatic Links in Excel 2003

We have recently upgraded from Office 2000 to Office 2003. When opening an Excel workbook in Excel 2003 (document created when we were using Excel 2000) and adding a new worksheet (eg summary sheet), and creating links through to cells on other sheets within the workbook, the links are not updating automatically. I have selected 'Automatic' in Tools, Options, Calculations. I have also got update 'Automatic' selected in Edit, Links.
Pressing F9 doesn't help. The only way to update the links is to close the document and re-open it (clicking on 'Update Links' when the option box appears), or, clicking in the cell that has not updated correctly, and pressing return.
Why are the links not updating automatically?
Can anyone help?