Error building Player: CommandInvokationFailure:

i have just a blank project with prime31 google play game services plugin in it and im trying to run the demo scene and i keep getting this error, i feel like its something simple like setting environment variables or something, any help is greatly appreciated thank you

Error building Player: CommandInvokationFailure: Unable to convert classes into dex format. See the Console for details. C:\Program Files (x86)\Java\jdk1.7.0_51\bin\java.exe -Xmx1024M -Dcom.android.sdkmanager.toolsdir="C:/Users/John P. Rowan III/android-sdks\tools" -Dfile.encoding=UTF8 -jar "C:/Program Files (x86)/Unity/Editor/Data/BuildTargetTools/AndroidPlayer\sdktools.jar" -

stderr[

UNEXPECTED TOP-LEVEL EXCEPTION: com.android.dx.cf.iface.ParseException: bad class file magic (00051607) or version (0000.0002) at com.android.dx.cf.direct.DirectClassFile.parse0(DirectClassFile.java:472) at com.android.dx.cf.direct.DirectClassFile.parse(DirectClassFile.java:406) at com.android.dx.cf.direct.DirectClassFile.parseToInterfacesIfNecessary(DirectClassFile.java:388) at com.android.dx.cf.direct.DirectClassFile.getMagic(DirectClassFile.java:251) at com.android.dx.command.dexer.Main.processClass(Main.java:665) at com.android.dx.command.dexer.Main.processFileBytes(Main.java:634) at com.android.dx.command.dexer.Main.access$600(Main.java:78) at com.android.dx.command.dexer.Main$1.processFileBytes(Main.java:572) at com.android.dx.cf.direct.ClassPathOpener.processArchive(ClassPathOpener.java:284) at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:166) at com.android.dx.cf.direct.ClassPathOpener.processDirectory(ClassPathOpener.java:229) at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:158) at com.android.dx.cf.direct.ClassPathOpener.process(ClassPathOpener.java:144) at com.android.dx.command.dexer.Main.processOne(Main.java:596) at com.android.dx.command.dexer.Main.processAllFiles(Main.java:498) at com.android.dx.command.dexer.Main.runMonoDex(Main.java:264) at com.android.dx.command.dexer.Main.run(Main.java:230) at com.android.dx.command.dexer.Main.main(Main.java:199) at com.android.dx.command.Main.main(Main.java:103) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at SDKMain.main(SDKMain.java:129) ...while parsing __MACOSX/com/google/android/gms/ads/._a.class

1 error; aborting