Recently, a minor flaw was discovered in the latest version of Microsoft Excel. While not a security vulnerability, it was still an issue that could cause problems with people relying on it as it would result in incorrect calculations. It affected only Office 2007, and was the type of bug you'd expect to never see in software this mature. It is not a flaw in the actual computation or the answer, but merely how it is displayed:

When you perform a calculation in Excel 2007, the following behavior occurs:
The result of the calculation is a number from 65534.99999999995 to 65535. The calculation is performed correctly. However, the result is incorrectly shown as 100000.

Either way, Microsoft has posted a fix for the math error including articles on how to install the fix. When the first service pack for Office 2007 is released, this will be one of the included fixes. This is being released in an usual fashion, outside of Microsoft's regular patch cycle