Inspiron 5520 15R windows 8.1 web cam problem

Yesterday , I updated from windows 7 to windows 8.1 and have installed latest web cam central and web cam driver and in the device manager it shows that webcam is working fine but when i run webcam central it shows this message """ close the other video streaming application to start video "" I have checked the task manager no other app except dell web cam central.  In conclusion web cam is not working, Please help !!!