Open multiple sessions with Selenium-ChromeDriver

Question

I have a Java application that uses Selenium-ChromeDriver to perform some automation tasks on a Windows system and I would like to run more than one instance simultaneously.

If just one instance of the program is running everything goes fine. If I start a second instance while the first one is running the browser is opened but the automation doesn't start. The browser shows a warning about disabling extensions in developer mode and I end up with a Java exception at this line:

RemoteWebDriver driver = new RemoteWebDriver(new URL("http://127.0.0.1:9515"), capabilities);

Here's the exception stack trace:

org.openqa.selenium.WebDriverException: unknown error: Chrome failed to start: exited normally (Driver info: chromedriver=2.13.307647 (5a7d0541ebc58e69994a6fb2ed930f45261f3c29),platform=Windows NT 6.1 SP1 x86_64) (WARNING: The server did not provide any stacktrace information) Command duration or timeout: 60.31 seconds Build info: version: '2.44.0', revision: '76d78cf323ce037c5f92db6c1bba601c2ac43ad8', time: '2014-10-23 13:11:40' System info: host: 'Remigio', ip: '172.31.50.221', os.name: 'Windows 7', os.arch: 'amd64', os.version: '6.1', java.version: '1.7.0_01' Driver info: org.openqa.selenium.remote.RemoteWebDriver at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:525) at org.openqa.selenium.remote.ErrorHandler.createThrowable(ErrorHandler.java:204) at org.openqa.selenium.remote.ErrorHandler.throwIfResponseFailed(ErrorHandler.java:156) at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:599) at org.openqa.selenium.remote.RemoteWebDriver.startSession(RemoteWebDriver.java:240) at org.openqa.selenium.remote.RemoteWebDriver.<init>(RemoteWebDriver.java:126) at org.openqa.selenium.remote.RemoteWebDriver.<init>(RemoteWebDriver.java:153)

I'm using a custom profile which is shared by the two instances and a ChromePortable binary. Both instances uses the same ChromeDriver.exe running under the default port 9515.

What I'm doing wrong?

Thanks!