Xcode Build failed : mach-o errors

Hello everyone here, I have been fighting this issue for severals days now without seeing the end of it.
I have created a simple game in unity 4.5, using only the EaseSave2 plugin. Everything is exported and runs perfectly in the iOS simulator. When I try to build in Xcode for an iOS device I get mach-O type errors. I have looked about one hundred pages on the internet with dozens of possible causes but none of them helped me to fix it.

I have tried to add libraries, re-install both Xcode and unity ( just to be sure ) and to export/import my assets into a new project - the results are the same. Note that if I create an empty project with only a sprite in background it builds correctly.

Thank you so much in advance !

Here are the errors :

Undefined symbols for architecture armv7:

"__showBannerAdTopRight", referenced from:

RegisterMonoModules() in RegisterMonoModules.o

"__showInterstitialAd", referenced from:

RegisterMonoModules() in RegisterMonoModules.o

"__initAds", referenced from:

RegisterMonoModules() in RegisterMonoModules.o

"__hideBannerAds", referenced from:

RegisterMonoModules() in RegisterMonoModules.o

ld: symbol(s) not found for architecture armv7

clang: error: linker command failed with exit code 1 (use -v to see invocation)

 

Did you do Replace build from Unity? (not Append)