WebDriver para Firefox: el navegador se inicia con una página vacía, se cuelga durante 2 minutos, se reinicia y luego se ejecuta la prueba. ¿Por qué?

Estoy tratando de actualizar mi conjunto de pruebas Java para usar Selenium 3 y geckodriver. Sin embargo, veo este comportamiento muy extraño al ejecutar el comando de prueba:

Firefox se abre en una página en blanco.Se queda así durante unos 2 minutos.Se cierra y luego se reinicia inmediatamente.La prueba corre y pasa.

Yo uso Selenium 3.0.1, geckodriver 0.11.1, Firefox 50.0 en Linux de 64 bits.

Obtengo FirefoxDriver así:

DesiredCapabilities capabilities = DesiredCapabilities.firefox();
capabilities.setCapability("marionette", true);
return new FirefoxDriver(capabilities);

Estoy configurando la propiedad del sistemawebdriver.gecko.driver en mi conf Maven:

<webdriver.gecko.driver>
  ${basedir}/src/test/resources/geckodriver
</webdriver.gecko.driver>

¿Qué me podría estar perdiendo? ¡Muchas gracias por cualquier ayuda!

Registros de consola para mis pruebas (con tres grupos de sincronización distintos):

alrededor de las 3:54:30 p.m.

Registro completo:https://justpaste.it/10qn9

Fragmentos clave:

Configuring TestNG with: TestNG652Configurator
[VerboseTestNG] RUNNING: Suite: "Surefire test" containing "1" Tests (config: null)
[VerboseTestNG] INVOKING CONFIGURATION: "Surefire test" - @BeforeClass com.example.MyTest.classSetUp()
[VerboseTestNG] PASSED CONFIGURATION: "Surefire test" - @BeforeClass com.example.MyTest.classSetUp() finished in 384 ms
[VerboseTestNG] INVOKING CONFIGURATION: "Surefire test" - @BeforeMethod com.example.MyTest.methodSetUp()
1479999268209   geckodriver INFO    Listening on 127.0.0.1:7263
Nov 24, 2016 3:54:28 PM org.openqa.selenium.remote.ProtocolHandshake createSession
INFO: Attempting bi-dialect session, assuming Postel's Law holds true on the remote end
1479999268435   mozprofile::profile INFO    Using profile path /tmp/rust_mozprofile.VYFzbHfCS7iH
1479999268438   geckodriver::marionette INFO    Starting browser /usr/bin/firefox
1479999268441   geckodriver::marionette INFO    Connecting to Marionette on localhost:56753
(firefox:2956): GLib-GObject-CRITICAL **: g_object_ref: assertion 'object->ref_count > 0' failed
(firefox:2956): GLib-GObject-CRITICAL **: g_object_unref: assertion 'object->ref_count > 0' failed
(firefox:2956): GLib-GObject-CRITICAL **: g_object_ref: assertion 'object->ref_count > 0' failed
(firefox:2956): GLib-GObject-CRITICAL **: g_object_unref: assertion 'object->ref_count > 0' failed
[...]
1479999269312   addons.manager  DEBUG   Completed startup sequence
1479999269598   Marionette  INFO    Listening on port 56753
1479999270046   addons.manager  DEBUG   Starting provider: <unnamed-provider>
1479999270046   addons.manager  DEBUG   Registering shutdown blocker for <unnamed-provider>
1479999270048   addons.manager  DEBUG   Provider finished startup: <unnamed-provider>
1479999270094   addons.manager  DEBUG   Starting provider: PreviousExperimentProvider
1479999270094   addons.manager  DEBUG   Registering shutdown blocker for PreviousExperimentProvider
1479999270095   addons.manager  DEBUG   Provider finished startup: PreviousExperimentProvider
1479999270100   DeferredSave.extensions.json    DEBUG   Starting write
1479999270286   DeferredSave.extensions.json    DEBUG   Write succeeded
1479999270288   addons.xpi-utils    DEBUG   XPI Database saved, setting schema version preference to 17
(/usr/lib/firefox/plugin-container:3019): GLib-GObject-CRITICAL **: g_object_ref: assertion 'object->ref_count > 0' failed
(/usr/lib/firefox/plugin-container:3019): GLib-GObject-CRITICAL **: g_object_unref: assertion 'object->ref_count > 0' failed
(/usr/lib/firefox/plugin-container:3019): GLib-GObject-CRITICAL **: g_object_ref: assertion 'object->ref_count > 0' failed
(/usr/lib/firefox/plugin-container:3019): GLib-GObject-CRITICAL **: g_object_unref: assertion 'object->ref_count > 0' failed
alrededor de las 3:55:32 p.m.

Registro completo:

1479999331434   addons.productaddons    INFO    sending request to: https://aus5.mozilla.org/update/3/GMP/50.0/20161114145022/Linux_x86_64-gcc3/null/release-cck- ubuntu/Linux%203.13.0-101-generic%20(GTK%203.10.8%2Clibpulse%204.0.0)/canonical/1.0/update.xml
1479999332144   addons.productaddons    INFO    Completed downloading document
1479999332573   addons.productaddons    INFO    downloadXHR File download. status=200
1479999332581   addons.productaddons    INFO    Downloaded file will be saved to /tmp/tmpaddon
alrededor de 3:56:35 PM

Registro completo:

Nov 24, 2016 3:56:35 PM org.openqa.selenium.remote.ProtocolHandshake createSession
INFO: Detected dialect: W3C
[VerboseTestNG] PASSED CONFIGURATION: "Surefire test" - @BeforeMethod com.example.MyTest.methodSetUp() finished in 129531 ms
[VerboseTestNG] INVOKING: "Surefire test" - com.example.MyTest.testSomething()
[VerboseTestNG] PASSED: "Surefire test" - com.example.MyTest.testSomething() finished in 1603 ms

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