FIX: Excel 2000 May Fault in MSO9.DLL When Calling an XLL Function that Takes an Array

Complex workbooks that require heavy recalculation may encounter a situation that can cause Excel 2000 to accidentally attempt to free an invalid address for an array of doubles being passed as an argument to an XLL function call, causing the Office library (Mso9.dll) to crash Excel and generate one of the following error messages: -or- The problem only occurs when very complex workbooks that make heavy use of custom XLLs are recalculated, and may not crash Excel even when it is hit based on the values that are inside the array.

The problem does not occur with public versions of Excel 97 (but may occur with some QFE versions), nor does it occur with Excel 2002.

When it prepares to call an XLL function during a recalculation, Excel calculates all dependent cells that are needed to produce the arguments to pass to the XLL function. If one of the dependent cell values is changed by outside code (such as DDE or Automation) after this calculation, but before the XLL function is called, Excel must postpone the XLL call and again recalculate the dependent cells.

Under this condition, if the dependent values are being passed as an array (XLOPER type = xltypeMulti|xltypeNum), Excel 2000 may improperly attempt to free an invalid memory block that is based on the contents of the array value preceding the uncalculated entry. This condition is very rare and cannot be reproduced on demand.

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, submit a request to Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language. The English version of this fix should have the following file attributes or later: After the hotfix is installed, the following files will have the listed attributes or later:

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.