Seems strange but if you are having trouble with Camera Control being unreliable or failing to perform, try making sure that your USB cable connection is good:
- Use a short cable
- Use the best quality cable you have
- Plug the cable directly into the PC, not via a hub
Strange as it may seem this has fixed some of my own problems. Apparently it is possible to have an unreliable USB connection which is good enough for some purposes (including downloading images in batches), but not good enough for tethering.
The details I don’t understand, but give it a try if all else fails.