Does this happen on the first iteration of that while loop or the second?
The layout of that VI is odd. You have a boolean that selects one VI or another. Okay. But then you proceed to open a reference to it, run it, and insert it into the subpanel on every iteration of the while loop. You should only be doing this once. You probably are getting the error when you try to run a VI that is already running from the previous iteration.
You an event structure that only runs when there is a value change on the boolean. Then remove the existing VI from the subpanel, stop running and close it. The open the other reference, insert it and run it.
