I started using the lovely json-framework for the iPhone but then suddenly found that if I compiled for anything greater than 2.1 for a device, that it would pop up with:

Codesign error: “object file format invalid or unsuitable”

It took me a long time to figure out what was going on, but thanks to a blog post, the fix is this:

On the project settings, on the build tab, search for “Code Signing Resource Rules Path” and set “$(SDKROOT)/ResourceRules.plist” as its value.

I’m not sure how it works as it looks like that is the path it already has, but hey, it seems to work!