Just what Microsoft doesn't need, in the middle of a rumble over Office: an exotic glitch in Excel 2007.

It seems like a joke that only math geeks would get, but it's true.

Excel 2007 fails to correctly multiply numbers "around 65,535," according to an explanation the company posted today. It said a fix is coming shortly, after it's tested to be sure it doesn't cause other problems.

Technically, the software is doing the calculation properly, but it's displaying an incorrect number to users who want to, say, multiply 5.1 by 12,850. From the explainer:

This issue was introduced when we were making changes to the Excel calculation logic in the Office 2007 time frame. Specifically, Excel incorrectly displays the result of a calculation in 12 very specific cases. ... The key here is that the issue is actually not in the calculation itself (the result of the calculation stored in Excel's memory is correct), but only in the result that is shown in the sheet. Said another way, =850*77.1 will display an incorrect value, but if you then multiply the result by 2, you will get the correct answer (i.e. if A1 contains "=850*77.1", and A2 contains "=A1*2", A2 will return the correct answer of 131,070).

The explanation is good, but as far as users are concerned, it doesn't work right.

Excel users are generally so invested in the product, they probably just want it fixed and won't dump the software. But you just know IBM's going to bring this up at every sales call for the next decade.