If I want to copy data from workbook into another workbook, I have always
used this formula in the destination workbook cell: "='workbook1'!D20" where
workbook1 is the name of the workbook and D20 is the row and column within
that workbook where the data is located.

This has always worked fine in Excel 2003.

In Excel 2007, it works sometimes. Other times it returns the formula as
the answer or it returns a 0 value. It does not appear to be consistant. If
I can get it to work it usually will continue to work.

Any ideas on what I am doing wroing.