Of course, you have to ensure that the library and the project using the library (here Codeblocks) have been built targetting the same architecture. So, did you use something related to the architecture (32-bit or 64-bit, Intel/Motorola PPC) in the framework of CFLAG/CXXFLAGS/LDFLAGS during configure of both wxWidgets and Code::Blocks (I mean something like "arch i386) ?
Second question : does OS X 10.8 still 32-bit able (don't know by myself since I'm under 10.6) ?