org.openqa.selenium.firefox.NotConnectedException: Unable to connect to host 127.0.0.1 on port 7055 after 45000 ms

I’m trying to run a Junit Test case which i exported from Selenium IDE. Im getting above exception.I’m using Windows XP,Firefox 20.0.1,and using selenium-server-standalone-2.28.0.jar.Upon run, a blank Firefox window is opened. When I close that window i get below exception in console This exception in JUnit Failure trace

error code: 523