Enable / Disable T&C task in Automation gives Microsoft Workflow Designer Object Reference error

Hi. I have an automation script that has several T&C tasks. For a couple of them, but not all of them: when I enable / disable a task, I get a pop-up window with the error "Microsoft Workflow Designer Object reference not set to an instance of an object" (I'm not running anything at this point, just enabling/disabling the task). I can run the script in Toad and it completes. However, when I'm running it in Microsoft Scheduler, it is going out to lunch and I have to boot my PC to kill the process. But I don't know if it s because of this Object Reference error or not. My T&C tasks go against local storage. I have written many, many automation scripts with T&C tasks and I haven't seen this error in any of them. I can open the T&C file, run the query, etc. without error. Thoughts?