Updated to xCode 4.5 and when time profiling my app Symbol Name doesn't show classes or objects anymore, but shows memory addresses see below.
0x2fd42e13
0x38014448
I used to see the following
main
NSManagedObjectContext
When I could see the class names then I can track down the issues in the extended detail. Now the extended detail shows the same thing as the 0x2fd42e13.