I grabbed the latest build today, but both Kitchen Sink and my app have white app icons in both emulator and on the device when I compiles them. I switch back to 1.3.2 and the icons show up.
I had this briefly today after updating my iPhone SDK from 4.0 to 4.0.1; seems to have cleared up after some fresh rebuilds. Try dumping the build/iphone directory and rebuilding?
same for me (with 4.0 SDK) deleting buid/iphone and just one rebuild solved my pb.