iOS - Linker error after upgrading to Xcode 4.5, possibly Core Plot related

By the looks of it you'll need to rebuild the libCorePlot library with Xcode 4.5GM so that there's a ARMV7S build of the library. Seems as if it's trying to use the version you built with the older Xcode.

I'm also using the Core Plot 1.0 static library in my project. I was able to address the problem by Setting Build Active Architectures Only to Yes. Build Active Architectures Only is in the Architecture section of the Target's Build Settings in Xcode.

I downloaded the Core Plot 1.0 zip file which seems to be incomplete so I cannot rebuild the libraries.

It works in the simulator because the simulator will always use i386 architecture. That hasn't changed with the new SDK. What has changed is the presence of the iPhone 5, which uses a new architecture (armv7s). The project for your app automatically added armv7s as a valid architecture, but the library was likely compiled without knowledge of it. Thus, your arm7s-enabled app tries to link against a library that was built without armv7s and fails.

To fix it, you'll just need access to the project that produces the library. Modify the "Valid Architecture" setting on the target to include armv7s, then rebuild.