Sleeper: XIRR #num! if I don't put a guess value?

[doctortt]

I was told that you don't need to enter a guess value and the XIRR function will work. However, I get #NUM! every time I leave the value blank. I did look it up, and Microsoft says that if you leave it blank, it will assume .10, which is 10%. I now have to manually enter a number as a dummy. I'm using Excel 2010. Does anyone have this issue or is it just me?

[Bob Phillips]

Tell us what data you are using and what you tried in specifics, and we can check.