我正在Windows 7上运行Selenium Standalone Server 2.25，并将Internet Explorer
9作为浏览器，对于需要打开浏览器的每个测试，都会遇到此错误：

Selenium::WebDriver::Error::UnknownError:
       Unable to get browser (WARNING: The server did not provide any stacktrace information)
       Command duration or timeout: 10 milliseconds
       Build info: version: '2.25.0', revision: '17482', time: '2012-07-18 21:08:56'
       System info: os.name: 'Windows 7', os.arch: 'x86', os.version: '6.1', java.version: '1.7.0_07'
       Driver info: driver.version: EventFiringWebDriver
       Session ID: 356e9fc8-2d2b-4808-964c-4a1fea7415f9 (org.openqa.selenium.WebDriverException)

我究竟做错了什么？完全相同的信息出现在Selenium Server控制台上。