TestBench issue

Hi All,
I have created a simple application using Vaadin and using VaadinTest bech for testing. When I play in FireFox Vaadin Recorder, it runs fine without any error but when I run as JUnit tests, I get the following errors. Is there any configuration or anything that I am missing?

Why am I getting this XPATH error, how and when these elements are changing? Should they be same as that of in the corded test file?
run-tests:
[junit]
Testsuite: Test1.osx_firefox36.Test2_Test1
[junit]
Tests run: 1, Failures: 1, Errors: 0, Time elapsed: 18.712 sec
[junit]

[junit]

Testcase: testosx_firefox36(Test2_Test1.osx_firefox36.Test2_Test1): FAILED
[junit]
Test2_Test1 failed at CommandNr = 10 with Cmd = mouseClick. Failure message = ERROR: Element vaadin=foo::/VVerticalLayout[0]
/ChildComponentContainer[1]
/VSplitPanelVertical[0]
/VVerticalLayout[0]
/ChildComponentContainer[0]
/VHorizontalLayout[0]
/ChildComponentContainer[1]
/VHorizontalLayout[0]
/ChildComponentContainer[1]
/VEmbedded[0]
/domChild[0]
not found
[junit]
junit.framework.AssertionFailedError: Test2_Test1 failed at CommandNr = 10 with Cmd = mouseClick. Failure message = ERROR: Element vaadin=foo::/VVerticalLayout[0]
/ChildComponentContainer[1]
/VSplitPanelVertical[0]
/VVerticalLayout[0]
/ChildComponentContainer[0]
/VHorizontalLayout[0]
/ChildComponentContainer[1]
/VHorizontalLayout[0]
/ChildComponentContainer[1]
/VEmbedded[0]
/domChild[0]
not found
[junit]
at Test2_Test1.osx_firefox36.Test2_Test1.internal_Test2_Test1(Test2_Test1.java:85)
[junit]
at Test2_Test1.osx_firefox36.Test2_Test1.testosx_firefox36(Test2_Test1.java:22)
[junit]
at com.thoughtworks.selenium.SeleneseTestCase.runBare(SeleneseTestCase.java:212)

I also get this session error.
[junit]

[junit]

[junit]

Test Test2_Test1.osx_firefox36.Test2_Test1 FAILED
[junit]
Testsuite: Test2_Test1.osx_googlechrome6.Test2_Test1
[junit]
Tests run: 1, Failures: 0, Errors: 1, Time elapsed: 0.365 sec
[junit]

[junit]

Testcase: testosx_googlechrome6(Test2_Test1.osx_googlechrome6.Test2_Test1): Caused an ERROR
[junit]
Could not start Selenium session: ERROR: Could not retrieve a new session
[junit]
java.lang.RuntimeException: Could not start Selenium session: ERROR: Could not retrieve a new session
[junit]
at com.thoughtworks.selenium.DefaultSelenium.start(DefaultSelenium.java:89)
[junit]
at com.vaadin.testbench.testcase.VaadinTestBase.setUp(VaadinTestBase.java:32)
[junit]
at com.vaadin.testbench.testcase.AbstractVaadinTestCase.setUp(AbstractVaadinTestCase.java:379)
[junit]
at Test2_Test1.osx_googlechrome6.Test2_Test1.testosx_googlechrome6(Test2_Test1.java:21)
[junit]
at com.thoughtworks.selenium.SeleneseTestCase.runBare(SeleneseTestCase.java:212)
[junit]
Caused by: com.thoughtworks.selenium.SeleniumException: ERROR: Could not retrieve a new session
[junit]
at com.thoughtworks.selenium.HttpCommandProcessor.throwAssertionFailureExceptionOrError(HttpCommandProcessor.java:97)
[junit]
at com.thoughtworks.selenium.HttpCommandProcessor.doCommand(HttpCommandProcessor.java:91)
[junit]
at com.thoughtworks.selenium.HttpCommandProcessor.getString(HttpCommandProcessor.java:262)
[junit]
at com.thoughtworks.selenium.HttpCommandProcessor.start(HttpCommandProcessor.java:223)
[junit]
at com.thoughtworks.selenium.DefaultSelenium.start(DefaultSelenium.java:81)

thanks
dheeraj