Xcode errors in CFString.h: "Using undeclared identifier" true ""

Question

I pulled my hair for errors that suddenly appeared in my Mac OS application (10.7). Build CFString.h: with multiple errors in CFString.h:

Use of undeclared identifier 'true'

CGGeometry.h :

 Function cannot return function of type 'bool' (aka 'int (int)') 

and much more...

Obviously, my project settings are wrong, but I played with the build settings, tried to make sure that I get attached to all the frameworks I need, cleans the build folder, restarts Xcode, reinstalls Xcode, starts a new project and drags all the files ... All still getting these errors! Other projects are compiled OK.

I have no idea why this is happening, so I'm not sure what other details are relevant, but I will be happy to provide any information necessary ...

Any help is much appreciated!