It has nothing to do with the python version. 2.7 is the stable proven version. The problem is related to desktops. The tool's code can't find the viewer. I've found using the Solaris desktop exclusively in a session is the most error free.
I would submit your specific desktop in a bug report so they can track down what is failing.
Edit: just tested switching desktops around back and forth and creating cameras and lights, and no problems. Is there more specific steps to recreate your problem?
Weird that this isn't more common. It pretty much always starts if I delete or exchange a node upstream of the currently viewed one. After that it will give me these errors for every click on a light or camera.
I'll guess I need to do some more investigating tomorrow.