XCode4 problems

Typical messages:

• At least one valid architecture arm6 must be present
• No architectures to compile for
• (ONLY_ACTIVE_ARCH=YES, active arch=i386, VALID_ARCHS=armv6)
• VALID_ARCHS=   (nil)

In Project Build Settings check Build Active Architecture Only and set to NO

You should also check the settings for Architectures and Valid Architectures

and add if necessary armv6 armv7

I have seen once or twice when creating a new project armv6f and armv7f

$(ARCHS_UNIVERSAL_IPHONE_OS) will build a universal iPhone/iPad app

If you set the architecture in the active target to armv7 and check the "Build Active Architecture Only" XCode will create a non-universal binary and you may end up with the proble above when you submit the app because of conflicting settings.