I had a similar problem when I switched from 3.2.5 to 3.2.6 .. all the frames turned red and no errors were found.
I tried restarting xcode, changed base sdk, etc., and didn't seem to fix it :(
To fix this, I had to do below (from some stream on the Internet, I can not find the source now).
1) go to your project directory/proj.xcodeproj (proj is your project name) 2) open up project.pbxproj file, using any text editor 3) search for "SDKROOT =", and modify it to point to your framework directory.
For me, I had to edit them: /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS4.3.sdk/
Save the pbxproj file before modifying it, just in case.
enjoy!
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