This is not an error as is indicated in multiple threads on this discussion board. (e.g. http://taskscheduler.codeplex.com/discussions/633848)
This was a setting provided for backwards compatibility with the V1 library where this setting works. Under V2, you must, as the exception states, use the InteractiveToken enum on the RegisterTaskDefinition instead of setting that property.
This was a setting provided for backwards compatibility with the V1 library where this setting works. Under V2, you must, as the exception states, use the InteractiveToken enum on the RegisterTaskDefinition instead of setting that property.