In My xcode project I had integrated XMPP framework. It works fine on iOS 5.1 simulator. When I tried to run the project on iOS 4.3 simulator I am getting an error.
Please see this Stackoverflow question : http://stackoverflow.com/questions/13027838/xmpp-not-working-on-ios-4-3-project
Not sure if it will solve your issue, but if your project is NOT ARC you have to tell the compiler to use ARC -fobjc-arc on the XMPP files, an not disable it like you currently are.
There's a wiki article about ARC:
(Sorry, I need to fix those broken images).
But like @ObjColumnist said, you need to use -fobjc-arc flag to tell the compiler the files are ARC.