Hrm... OK, I'm not sure then what the problem is. I suspect it's still somewhere in the event handlers for the form. I think, at this point, I'd contact SmartBear support directly and see if they can give you some insight.
I get the same error... not immediately on TC start up, but when I try to open a keyword test. So, defintiely something in the extension itself.
Did you find the cause of the error in the extension?
Is there any update on this issue you can share?