Somewhere in my code, I did some mistake by assigning NSNumber to NSString:
self.totalLikesLabel.text=[user objectForKey:@"totalLikes"];

When the app crashes at the point above, 5.1 Simulator did not show specific information of what lines in my code cause the crash. However, 4.3 Simulator did!
Do I have to configure some settings in 5.1 Simulator to have it working like 4.3 in this case?
This should let you see a little more than SIGABRT.