Try deleting com.apple.FaceTime.plist in Preferences folder.

Repairing permissions might help.

Open Disk Utility, select disk that contains OS that you use (e.g: Macintosh HD) and then click First Aid tab. Under First Aid you can:

Verify Disk Permissions
Repair Disk Permissions
Verify Disk
Repair Disk

Have u tried to force quit the problematic app?

Then force quit the Finder by relaunching?

Have u tried to switch off the mac then restarting?

Some easily done task if haven't tried yet..

P.s. One of the USB was being quirky before. Tried a lot of stuff then finally I switch the rMBP. It was all good after that.

All the best..

Try creating a new user account in System Preferences. See if you have the same problem with the new account.

If you're still interested in going at it, trace the Facetime log and paste it here. Here's how to find your logs.

http://apple.stackexchange.com/questions/2...d-my-crash-logs

Export the FaceTime log, upload it somewhere then send the link to me.

Try this - http://www.howtoisolve.com/how-to-solve-ns...-os-x-yosemite/

My MBP 15 2014 + 750M GC  has this issue  , any solution?

and also, i faced when i plug in my ip6+ into one of my usb, it will disconnect/connect rapidly 

then, itunes keep spamming dialog message : device could not connected. But it work well with another usb 

when is the best time to charge your mac ? Did a bit of study .... Shouldn't let it discharge below 15-20% .... My only doubt is they recommend to plugged in if socket comes in handy .... But always charging it is bad also so ? How long should I plugged in even its already 100% ....

Trying to maximise my battery lifespan ...