protractor: PhantomJS sometimes crashes

I have been successfully running a fairly comprehensive suite of Protractor e2e tests using Chrome on OSX (Mavericks: 10.9.2).

We have a technical requirement to run these tests headlessly, so I swapped in PhantomJS instead of Chrome, and after 20 seconds (consistently), I get the following error:

Runner Process Exited With Error Code: 8
Fatal error: protractor exited with code: 1

Now for some more detailed information.

Here is the full error output from the grunt task I am running:

Running "protractor:phantomjs" (protractor) task
------------------------------------
PID: 9678 (capability: phantomjs #1)
------------------------------------
Starting selenium standalone server...
Selenium standalone server started at http://192.168.1.111:4444/wd/hub
/path/node_modules/protractor/node_modules/selenium-webdriver/lib/webdriver/promise.js:1562
throw error;
^
UnknownError: null
at new bot.Error (/path/node_modules/protractor/node_modules/selenium-webdriver/lib/atoms/error.js:109:18)
at Object.bot.response.checkResponse (/path/node_modules/protractor/node_modules/selenium-webdriver/lib/atoms/response.js:106:9)
at /path/node_modules/protractor/node_modules/selenium-webdriver/lib/webdriver/webdriver.js:135:24
at /path/node_modules/protractor/node_modules/selenium-webdriver/lib/goog/base.js:1178:15
at webdriver.promise.ControlFlow.runInNewFrame_ (/path/node_modules/protractor/node_modules/selenium-webdriver/lib/webdriver/promise.js:1455:20)
at notify (/path/node_modules/protractor/node_modules/selenium-webdriver/lib/webdriver/promise.js:328:12)
at notifyAll (/path/node_modules/protractor/node_modules/selenium-webdriver/lib/webdriver/promise.js:297:7)
at fulfill (/path/node_modules/protractor/node_modules/selenium-webdriver/lib/webdriver/promise.js:402:7)
at /path/node_modules/protractor/node_modules/selenium-webdriver/lib/goog/base.js:1178:15
at webdriver.promise.ControlFlow.runInNewFrame_ (/path/node_modules/protractor/node_modules/selenium-webdriver/lib/webdriver/promise.js:1455:20)
==== async task ====
    WebDriver.createSession()
at Function.webdriver.WebDriver.acquireSession_ (/path/node_modules/protractor/node_modules/selenium-webdriver/lib/webdriver/webdriver.js:132:49)
at Function.webdriver.WebDriver.createSession (/path/node_modules/protractor/node_modules/selenium-webdriver/lib/webdriver/webdriver.js:111:30)
at Builder.build (/path/node_modules/protractor/node_modules/selenium-webdriver/builder.js:105:20)
at LocalDriverProvider.getDriver (/path/node_modules/protractor/lib/driverProviders/local.dp.js:128:9)
at /path/node_modules/protractor/lib/runner.js:327:35
at _fulfilled (/path/node_modules/protractor/node_modules/q/q.js:797:54)
at self.promiseDispatch.done (/path/node_modules/protractor/node_modules/q/q.js:826:30)
at Promise.promise.promiseDispatch (/path/node_modules/protractor/node_modules/q/q.js:759:13)
at /path/node_modules/protractor/node_modules/q/q.js:573:44
    [launcher] Runner Process Exited With Error Code: 8
>>
Fatal error: protractor exited with code: 1

Package versions:

"grunt-protractor-runner": "~0.2.3"
"protractor": "0.19.0"
"selenium-webdriver": "~2.40"

Contents of protractor.conf.js:

exports.config = {
    seleniumServerJar: '../../node_modules/protractor/selenium/selenium-server-standalone-2.39.0.jar',
    seleniumPort: 4444,
    seleniumArgs: ['-browserTimeout=60'],
    specs: [
        '../e2e/utils.js',
        '../e2e/**/*-suite.js'
    ],
    capabilities: {
        browserName: 'phantomjs',
        'phantomjs.binary.path': './node_modules/karma-phantomjs-launcher/node_modules/phantomjs/bin/phantomjs',
        'phantomjs.cli.args': ['--debug=true', '--webdriver', '--webdriver-logfile=webdriver.log', '--webdriver-loglevel=DEBUG']
    },
    baseUrl: 'http://localhost:9292',
    rootElement: 'body',
    onPrepare: function () {
        require('jasmine-reporters');
        jasmine.getEnv().addReporter(new jasmine.JUnitXmlReporter('test/results/', true, true));
    },
    framework: 'jasmine',
    jasmineNodeOpts: {
        onComplete: function () {
        },
        isVerbose: true,
        showColors: true,
        includeStackTrace: true,
        defaultTimeoutInterval: 30000
    }
};

I have tried installing version ~1.9.7-1 of the phantomjs package independently of the one that protractor depends upon, and updating the phantomjs.binary.path property in protractor.conf.js, but I get the same result.

After spending far too long debugging the JS to try to isolate where the error is occurring, I know that it is falling over in runner.js.

Specifically in Runner.prototype.runJasmine_(), the anonymous function passed to webdriver.promise.controlFlow().execute() here is never executed.

Can anyone help?

Let me know if you need more information.

Matt