After downloading a security update of Microsoft Office 2010, I am unable use ChemDraw for Excel.
Microsoft has released a security update (KB 2598039) which is creating problem in getting the ChemOffice Add-Ins loaded in Microsoft Excel 2010. Please click on the Microsoft's link below to view the information.
According to Microsoft:
You install this security update on a computer that has a third-party software solution installed. The software solution is based on Microsoft Visual Basic for Applications (VBA). The software solution creates an instance of the control directly through Microsoft Office. In this scenario, the control may not load in your solution.
To resolve this issue, delete the cached versions of the control type libraries (extender files) on the client computer. To do this, search your hard disk for files that have the ".exd" file name extension and delete all the .exd files that you find. These .exd files will be re-created automatically when you use the new controls the next time that you use VBA. These extender files will be under the user's profile and may also be in other locations, such as the following:
C:\documents and settings\username\Application Data\Microsoft\Forms
C:\documents and settings\username\AppData\Local\Temp\VBE