it’s strange that so many people have problems with the 3.1.4 version. I do not have any of those.
All those libraries you mentioned are there and working in my projects. I did a complete 3.1.3 deinstall with the Apple provided shell script. After that during 3.1.4 installation i chose cutomized install and activated all SDKS down to 2.0 (they are not installed by default)
Maybe thats the reason for me troubleless XCode 3.1.4 ?
I had this problem today. Fixed it by going into the Unity iPhone app in Applicaitons, right click and then select Show Package Contents. Navigate to Content>Frameworks>iPhone-Trampoline and then open the Unity-iPhone.xcodeprog.
Then in xcode I went to Project>Edit Project Settings and under Base SDK it was looking for the 2.0 version of the SDK. Click the arrow next to Base SDK and select 3.0, or 3.1, whatever you want to build against. Save the project then Build in Unity and it should work. Fixed it for me.
I had to do this in the xcode project in the trampolin folder of iphone unity installation. Otherwise it might switch back to older/previous sdk showing the “missing release” behaviour. Actually this happend to me with xcode 3.2.