Error: "Class not registered" when running SQL Tuning. (15631)

When I launch SQL Tuning from TOAD I get the error message "Class not registered" followed by an Access Violation message.

1. The license key used to register Toad does not have the SQL Tuning module activated. Review the activated options by selecting Help | About.

2. The Xpert Edition of Toad is not installed. The Xpert Edition of Toad can be downloaded from SupportLink (only applies to version 8.0 and below).

3. Rename current QPRB.DLL and replace with new QPRB.DLL of the same version. The QPRB.DLL is located in the TOAD install directory |Tuning_Lab folder. Make sure Toad and Tuning is closed before replacing the dll. After replacing the dll, launch Toad and test Tuning again.

A copy of the dll file can be retrieved from another working copy of Toad of the same version. Attached are QPRB.DLL for Toad 8.5.3 and 8.6.1.

4. Microsoft's XML Parser is not installed, which is required to launch the SQL Tuning Module. The XML Parser can be downloaded from http://www.microsoft.com/downloads/details.aspx?FamilyID=3144b72b-b4f2-46da-b4b6-c5d7485f2b42&displaylang=en.

5. Uninstall Tuning module by running Unwise.exe located in the Tuning_Lab subdirectory of Toad home directory.  Run ToadSQLTuning.exe from the same subdirectory to reinstall it.