I had a problem on my laptop (64 bit Win8.1) : every time I tried to access the webcam, pd crashed. Desktop and win7 laptop - no problem.
After reinstalling, running under compatibility mode etc I uninstalled pd-extended 0.43.4 and tried some earlier versions. Currently I am having much better success with 0.39.3.
I don't know if this would overcome your problem and I haven't had time to try and analyse which element is causing the issue.