I am seeing the #NUM! message all the time in the XIRR cells and the #VALUE!
message occasionally when I change parameters that affect the cell with the
circular reference. Interestingly, when I save the file in Excel 2008 and
then reopen in Excel 2007, the same errors occur - however when I retype the
formulae in Excel 2007 (exactly as they were before), it catches up and
recalculates ok. Then when I save the file again in Excel 2007, and re-open
it in Excel 2008, the same problem occurs again. Looks like my in investment
in Parallels was a good one, at least until the first fixes become available
for Office 2008.