Some of the fixes that the links Saif contain may work for some, but not for me.
I have a very simple solution without restarting that will usually get you through the day.
When you get this error, before you do anything else, build for the other device (if you are running a universal application).
When you build for the other device, it kind of "overwrites" the process that creates this error. Once the other device is up and running, immediately build for the device that created the error. This will work most if not all the time, and will save you time digging through the multitude of fixes you will find in the other links.
I tried almost all of the fixes found there and none of them worked in my case. This works, but you should check your appDelegate for any bugs in your willEnter/didEnter (and other related methods).