JScript error in XVal, Has anybody seen this error?

Microsoft JScript runtime error: 'this.Plugins[...]' is null or not an object

coming from this code:

var xVal = xVal || {
    Plugins: {},
    AttachValidator: function(elementPrefix, rulesConfig, p开发者_高级运维luginName) {
        if (pluginName != null)
            this.Plugins[pluginName].AttachValidator(elementPrefix, rulesConfig);
        else
            for (var key in this.Plugins) {
                this.Plugins[key].AttachValidator(elementPrefix, rulesConfig);
                return;
            }
    }
};

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Make sure you are referencing xVal.AspNetNative.js AND xVal.jquery.validate.js in your master page.