Kurt Shintaku's Blog

A customer pointed this out to me the other day:

Excel 2007 Bug Displays Wrong Result
September 26th, 2007
http://blogs.pcworld.com/staffblog/archives/005532.html

The issue is that in some situations, running certain calculations involving a resulting sum of 65535 can result in incorrect results.  Obviously, this has been patched since September and was documented on the Excel blog along with the release of the patch on October 9th.

Calculation Issue Update (Fix Available)
October 9th, 2007
http://blogs.msdn.com/excel/archive/2007/10/09/calculation-issue-update-fix-available.aspx

It is noted by some folks online that the hotfix will not install correctly unless you have Windows Installer 3.1 v2 on your machine.

Windows Installer 3.1 v2 (KB893803)
http://support.microsoft.com/kb/893803

In case you’re interested, a 3rd party literally disassembled Excel 2007 and has written a paper about what originally caused the bug and how the hotfix fixes the problem.

Chris Lomont’s Analysis of the Q943075 bug
"I show why precisely the 12 values format incorrectly, what changed from earlier versions, and how the hotfix corrects the bug."
http://www.lomont.org/Math/Papers/2007/Excel2007/Excel2007Bug.pdf

The hotfix is of course available as part of Office 2007 Service Pack 1.

2007 Microsoft Office Suite Service Pack 1 (218.3MB)
http://www.microsoft.com/downloads/details.aspx?FamilyId=9EC51594-992C-4165-A997-25DA01F388F5&displaylang=en