SOLUTION!!! -- Error 1608: Unable to create InstallDriver instance
If the multi-step solution Macrovision has published does not work for you (like it didn't work for me),
run RegSvr32 %WinDir%\System32\oleaut32.dll
The cause (or so I suspect)... InstallShield inappropriately unregisters
oleaut32.dll when it removes a program containing VBRunTime.
I watched this problem present itself on an uninstall of a 10.5 application. The specific key set removed from the registry is: