I am using CocoaPods to install the AFNetworking library. Here is my simple CocoaPods file:
platform :ios pod \'FMDB\' pod \'AFNetworking\'
Specifying your Versions of the desired pods may help.
platform :ios, '6.0' pod 'FMDB', '~> 2.0' pod 'AFNetworking', '~> 1.1.0'
Also make sure you're opening the correct xcworkspace file.
xcworkspace