I have installed AFNetworking 2.1.0 with CocoaPods on Xcode 5.
2014-02-07 11:55:19.984 OPS[1717:60b] *** Terminating app
due to uncaught exception'NSInvalidArgumentException',
unrecognized selector sent to instance 0x147b06d0'
I had the same problem with Xcode 5, Cocoapods and AFNetworking 1.3.3.
I found my answer in this Google Groups discussion: AFNetworking unrecognized selector
Make sure your project and target settings aren't overwriting the values in the xcconfig file.
Each level should have (at least) $(inherited) to inherit the settings of the parent.
In Build Settings, make sure you have
$(inherited) in Other Linker Flags.
Build Settings before I added
$(inherited) (choose Levels, not Combined):
Build Settings after I added
That fixed it for me.