Here is a brief explanation of the Excel 2007 formatting bug
Excel 2007 contains a formatting bug, rendering 850*77.1 as 100000 instead of 65535. This was discovered around Sept 22, 2007.
Once this was making the rounds on the Internet, 12 values were found to format incorrectly.
I explain how this happens through disassembly and code analysis in the above PDF document.
Here is the faulty routine call graph. Click for a LARGE version.