GLASSFISH 4 ERROR ON DEPLOYMENT

Hi,
I get below error when I redeploy. Please help

Error occurred during deployment: Keys cannot be duplicate. Old value of this key property, nullwill be retained.

Please see server.log for more details.

java.lang.LinkageError: loader (instance of org/glassfish/web/loader/WebappClassLoader): attempted duplicate class definition for name: "org/glassfish/web/loader/JdbcLeakPrevention"