Apparently Excel 2007 has a nice multiplication bug that you should all be aware of in case you decide to be foolish enough to run Excel 2007. Here's how to reproduce it (unfortunately I don't have access to Excel 2007, so I can't verify personally:
= 850 * 77.1
If you have the bug, Excel displays the result as 100,000. The correct answer is 65,535.
If you're seeing this bug, you can wait for a patch from Microsoft, or use the freely available patch located here.
Hope this helps!