Are you running your scripts through the MGC PCB Command Window or through MGC Launch?
Environment variables are no longer set while installing or running the VX tools to allow for side by side installation. To get around this, you run your compiled automation code through the MGC PCB Command Window or wrap it using MGC Launch. These set up temporary environment variables for our programs to use when working with the COM objects, if not...PDB Editor has no clue which version of VX you want it to launch and fails.