Q: iSight camera not working after installed Mavericks

My system information detected isight camera.

But couldn't use the camera on facetime, photobooth, skype or any other software.

I need to logoff my account and sign in back then only can use the camera.

Once i put my macbook to sleep, i'm unable to use the camera unless i logoff again.

I'm using macbook air mid 2011 model.

I've attached a screenshot where you can see the device detected by System Information.

But not in Facetime or photobooth.

Any advice?

Thanks in advance.