Excel Subtotal Yields Blank Results

[Mark]

Have a data range containing headers on the first row and numbers
below.

When I create a subtotal, Excel inserts the subtotal() function.
The grandtotal line contains valid sums for all but the four right
most columns. The four right most columns' grandtotals are blank.
They contain the subtotal() function in the same syntax as the other
cells to the left.

Any ideas what the problem might be in these four columns?

Thanks, Mark