Pivot Table data inconsistency

This can't occur very often, surely.....

I've just experienced a situation where my pivot table subtotals don't reconcile with grand totals. Admittedly, the worksheet it references is quite large (>35,000 rows), but I would have assumed it wasn't too large to pivot, otherwise I would have presented with a whole slew of error messages, in typical microsoft fashion, right?

I'll upload a file to show you what I mean (truncated version, but same error)

I'm just simply stumped eh....what a freak occurrence

[solved: some of the independent variables were common to the dependent variables and the overlap explains the discrepancy...it's not Excel's fault]