Ashley
Ok. I found the bug and a workaround it. It seems something is not initialized at least on my PCs (3 tested PCs)
So the workaround for my problem is I have to do this.
1)Open any problematic physic project.
2)Click on Export
3)Select CocoonJS
4)When CocoonJS dialog appear , just click cancel to close the dialog.
5)Now preview via WiFi will work every time.
If I close the project, I need to repeat the above steps. I can reproduce this bug with the example or demo project and also some of my physic projects that are not working previously.
I tested on
Windows 8 64bit
2 Windows 7 SP1 64Bit
I found this bug since R139 (before that I didn't test it).
Regards