Formula displays result in formula box but not in cell
 

I have a circular worksheet resulting in an IRR calculation using the XIRR
formula. (The iteration box is checked.) The correct numerical result is
displayed in the formula argument box, but the cell displays #VALUE. Also,
when I break the circular reference the correct answer displays in the cell
as well. However, I need the circularlity to make the worksheet useful.

Any ideas on why this would happen. As I said, it is clear that Excel can
do the math despite the circularity, because the result shows in the formula
argument box. However, the circularity seems to be causing a problem with
the output displayed in the cell.