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 ools” -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

Hello PAL,

All you need to do is correctly select your Keystore.

Incase its already set up, set it up again and double check the alias for it (from the dropdown)