Microsoft Hotfix 971138 is required for Autodesk Inventor add-Ins to run successfully on Windows Vista. This problem may also affect Inventor Third-Party add-ins.
In most install scenarios, the user will be prevented from installing Autodesk Inventor 2012 on Windows Vista without first installing the Microsoft Hotfix. However, in certain scenarios, particularly when installing via network deployments, it is possible to Install Autodesk Inventor 2012 without first installing the hotfix.
Uninstalling the Microsoft Hotfix KB971138 after Inventor 2012 is installed will also result in Inventor Add-ins not functioning properly. The add-in behavior without the Microsoft Hotfix may vary from user to user. Common behaviors include missing add-ins from the add-in manager or add-ins being greyed out in the Inventor UI even though they are listed in the Add-in Manager as being registered.
This problem affects all Versions of Windows Vista ONLY. Windows XP and Windows 7 are not affected by this problem.
To solve the issue, install Microsoft hotfix 971138. This hotfix is available from Microsoft at http://support.microsoft.com/kb/971138.
You will need to request the hotfix from Microsoft by registering with a valid email address following the instructions at the hotfix site. Microsoft will then send an email containing a link and password allowing access to the hotfix download.