I have made an iPhone app with localized versions. It mostly works fine, but there are two views in which localized NIBs do not load. Standard NIBs (in English) are used. I
Another one for the simulator on SDK 4.0 - delete the application on the simulator, build -> clean all targets in XCode and restart
I had a similar issue on the Simulator. Cleaning all targets helped me. Give it a try.
On the simulator I had to use "iOS Simulator" -> "Reset Content and Settings"
Answer is: reboot the iPhone.