org.openqa.selenium.remote.UnreachableBrowserException: Could not start a new session.

 This type of error will come just in case

1) if you script unable to find xpath which  you have specified.

To trobleshoot this error .. run your script on Debug mode. So that you will come to know.. where it is failing.
2) just in case if you are driver is close before performing your operations in that case also this error will come.




org.openqa.selenium.remote.UnreachableBrowserException: Could not start a new session. Possible causes are invalid address of the remote server or browser start-up failure.
Build info: version: '2.31.0', revision: '1bd294d185a80fa4206dfeab80ba773c04ac33c0', time: '2013-02-27 13:51:26'
System info: os.name: 'Windows 7', os.arch: 'amd64', os.version: '6.1', java.version: '1.7.0_21'
Driver info: driver.version: ChromeDriver
    at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:548)
    at org.openqa.selenium.remote.RemoteWebDriver.startSession(RemoteWebDriver.java:216)
    at org.openqa.selenium.remote.RemoteWebDriver.<init>(RemoteWebDriver.java:111)
    at org.openqa.selenium.remote.RemoteWebDriver.<init>(RemoteWebDriver.java:115)
    at org.openqa.selenium.chrome.ChromeDriver.<init>(ChromeDriver.java:161)
    at org.openqa.selenium.chrome.ChromeDriver.<init>(ChromeDriver.java:107)
    at com.mns.international.framework.WebDriverLoader.initializeWebDriver(WebDriverLoader.java:61)
    at testsuites.MyFirstTest.beforetest(MyFirstTest.java:40)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:27)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
    at org.junit.rules.Verifier$1.evaluate(Verifier.java:34)
    at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49)
    at org.junit.runners.ParentRunner