A bug in this week's MS08-014 patch causes Excel to return zeroes instead of the correct number when certain types of macros are run within the program.
The issue, which does not affect all Excel users, messes up calculations for Office Excel 2003 users who are grabbing data such as stock quotes or inventory levels from sources in real time and plugging them into an Excel array.
"If you have applications that leverage Real Time Data sources in Visual Basic for Applications functions, we recommend that you perform additional testing before initiating a wide deployment of the update," Microsoft said in an updated frequently-asked-questions section of the bulletin on the MS08-014 update.