第一个测试用例总是在selenium webdriver测试套件运行中失败

Question

在Nunit测试套件中运行持续集成，每次第一个测试用例都失败并出现以下错误：

SetUp : OpenQA.Selenium.WebDriverException : The HTTP request to the remote WebDriver server for URL http://localhost:7055/hub/session/384a1a60-4ed3-4cac-8143-265aa63ec980/url timed out after 60 seconds.
 ----> System.Net.WebException : The operation has timed out
TearDown : System.NullReferenceException : Object reference not set to an instance of an object.]]>

服务器有Windows8服务器和Mozilla firefox v 21

代码是：

#region TestSetup
[SetUp]
public void Setup()
{
    browser = ConfigurationHelper.GetWebDriver();
    browser.Navigate().GoToUrl(ConfigurationHelper.GetConsumerBankingURL());
    browser.Manage().Window.Maximize();
    loginPage = new LoginPage(browser);
    user = VoyagerHelper.EnrollUser();
    //The user should be able to successfully logged into the system. The default destination page shows up
    financialOverviewPage = loginPage.Login(user.UserName, ConfigurationBase.DefaultPassword) as FinancialOverviewPage;
    accountNumbers = financialOverviewPage.GetAccountNumber();
}
#endregion

#region TestTearDown

[TearDown]
public void TearDown()
{
    try
    {
        financialOverviewPage.Logout();
    }
    finally
    {
        browser.Quit();
    }
}
#endregion