I use SumProduct copiously throughout my spreadsheet, and for earlier rows it works fine. But from Row 4789 it fails.

If I manually re-type in the formula, it works; but if I dopy it down (from the previous row(s) it does not - although the formula is still in the cell, the numerical value is that of the row above. This repeats since (to row 4795 so far).

I have attempted to create an abbreviated spreadsheet of just the last dozen rows or so, but cannot. I do have a link to my whole spreadsheet in DropBox: https://www.dropbox.com/s/u128eu2uxc...ards.xlsm?dl=0 if that helps.

For example: =SUMPRODUCT($AH$2:$MT$2,$AH4789:$MT4789)*17.2+(MV4789+MW4789)*17.2 sows the previous row's number

But =SUMPRODUCT($HE$5:$HY$5,$HE4789:$HY4789)*38.9+MX4789*38.9 works fine

I'd appreciate some ideas on how to trace this fault.