[Greg McKaskle]

Actually, the open requires the channel to be wired. Check each Motor open and see that you have the channels wired that you meant to.

If you are using the drive VIs, check those opens. If using servos, check those too.

Finally, the next time you run, make sure the dashboard is open. It will show you if you have errors. I suspect that you have an issue where a channel is already in use, produces an error, and then the refnum is invalid.

Greg McKaskle