OK、私が思いついた本当のバグ修正です。 
以下を置き換えて/skin/frontend/base/default/js/opcheckout.js、setMethod()メソッドを編集および編集します。
setMethod: function(){
    if ($('login:guest') && $('login:guest').checked) {
        this.method = 'guest';
        new Ajax.Request(
            this.saveMethodUrl,
            {method: 'post', onFailure: this.ajaxFailure.bind(this), parameters: {method:'guest'}}
        );
        Element.hide('register-customer-password');
        this.gotoSection('billing', true);
    }
    else if($('login:register') && ($('login:register').checked || $('login:register').type == 'hidden')) {
        this.method = 'register';
        new Ajax.Request(
            this.saveMethodUrl,
            {method: 'post', onFailure: this.ajaxFailure.bind(this), parameters: {method:'register'}}
        );
        Element.show('register-customer-password');
        this.gotoSection('billing', true);
    }
    else{
        alert(Translator.translate('Please choose to register or to checkout as a guest').stripTags());
        return false;
    }
    document.body.fire('login:setMethod', {method : this.method});
},
と:
setMethod: function(){
    var formKey = $('checkout-step-login').select('[name=form_key]')[0].value;
    if ($('login:guest') && $('login:guest').checked) {
        this.method = 'guest';
        new Ajax.Request(
            this.saveMethodUrl,
            {method: 'post', onFailure: this.ajaxFailure.bind(this), parameters: {method:'guest', form_key:formKey}}
        );
        Element.hide('register-customer-password');
        this.gotoSection('billing', true);
    }
    else if($('login:register') && ($('login:register').checked || $('login:register').type == 'hidden')) {
        this.method = 'register';
        new Ajax.Request(
            this.saveMethodUrl,
            {method: 'post', onFailure: this.ajaxFailure.bind(this), parameters: {method:'register', form_key:formKey}}
        );
        Element.show('register-customer-password');
        this.gotoSection('billing', true);
    }
    else{
        alert(Translator.translate('Please choose to register or to checkout as a guest').stripTags());
        return false;
    }
    document.body.fire('login:setMethod', {method : this.method});
},
パッチのv2を待っている間にそれを行います