i am using the new xcode 4.5, i have this lines of code on some view controller:
DiscoverCell* cell=[table dequeueReusableCellWithIdentifier:@\"DiscoverCell\
For me it was a combination of the comment by Jason Coco and the answer by tomgerhardt: My app targets iOS5, I upgraded to Xcode 4.5 and created a new NIB. By default this targeted iOS6, causing a crash. I set this to iOS5 in the NIB's file inspector window.
Then I got a compiler error that told me Use Autolayout wasn't supported for iOS5, turned that of in the Document inspector and my issue was fixed.