If you multiply 850 by 77.1, the result should be 65535. However, Office 2007’s computations gives out an answer of 10000.

Try it yourselves:

=(850*77.1)
=SUMPRODUCT(850,77.1)
=SUMPRODUCT(850,77.1,2,0.5)

Here’s what you’ll get with Excel 2007

While that may not be serious to you, it is obvious that businesses using Excel 2007 for tabulations and computations have their data at risk, if not already compromised. Although such bugs have been reported to Microsoft long ago, there is still no reply as to how they will respond to these bugs. A quick look at the Office patch site shows patches only for security risks that certainly do not address these problems.

Several other reports coughed up the following syntaxes:
=5.1*12850
=10.2*6425
=20.4*3212.5
=40.8*1606.25
=77.1*850
=154.2*425
=212.5*308.4
=308.4*212.5
=425*154.2

The discussion that brought this up in the open was started at the Microsoft Public Excel Google Group and you can find more errors there. While Microsoft decides to stay silent at the topic, several people I know are already migrating to Open Office and it’s spreadsheet application or downgrading their Office Suites.