how to fix the updating issues from ios4.2 to ios5?

Question

I try to change the app which is in 4 to 5, during the build it shows the error like below.
Can any one give the solution for this?

Undefined symbols for architecture i386:
  "_OBJC_CLASS_$_FlurryAPI", referenced from:
      objc-class-ref in NewsViewController.o
      objc-class-ref in NewsDetailViewController.o
      objc-class-ref in ArchiveIndvidualView.o
      objc-class-ref in ArchiveMenuViewController.o
      objc-class-ref in ReleaseDetailView.o
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)