Version 6.1 - Unsupported major.minor version

[apparatusdeus]

I've recently upgrade to version 6.1 and I keep getting this error.

15:08:41 [SEVERE] Could not load 'plugins/SQLibrary.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: lib/PatPeter/SQLibrary/SQLibrary : Unsupported major.minor version 51.0

[apparatusdeus]

Nevermind, I realised the the error relates to a conflict between the Java compiler version and the Java version running on my machine. Once I switched to using Java Version 7 the error disappeared.