This is an error that I have mostly seen on 64 bit iOS devices and can happen if multiple threads read and change a variable under ARC. For example, I fixed a crash today where multiple background threads were reading and using a static NSDate and NSString variable and updating them without doing any kind of locking or queueing.
Using core data objects on multiple threads can also cause this crash, as I have seen many times in my crash logs.
I also use Crittercism, and this particular crash was a SEGV_ACCERR that only affected 64 bit devices.