This is something that has cost me several hours after I upgraded to iPhone SDK 2.2. I have also documented it in the iPhone Discussion Forum but here is a brief summary.
If you going to use the JSON framework with the iPhone SDK 2.2 then there will be some problems. I could no longer link the framework to my application. For some reason Apple has changed the code signing behaviour. To get around it you need to add the JSON framework source code to your XCode project.
1. Get the source code from:
svn checkout http://json-framework.googlecode.com/svn/trunk/ json-framework-read-only
2. Then copy that source code into your project directory (or use XCode add existing file...).
3. Where you used :
now you have to use:
and (as Dom pointed out)#import "SBJSON.h"
4. Build should be OK now.
Check out also http://jtribe.blogspot.com/2008/11/json-and-restful-web-services-on-iphone.html for more JSON / iPhone information.