I\'m getting this error:
tests.IntegrationTests.Selenium.RegisterAndLogin (TestFixtureSetUp):
SetUp : OpenQA.Selenium.WebDriverException : Failed to start up
1) Downgrade your firefox to < 19 because if i remember correctly WebDriver 2.33 support maxim Firefox 19
2)
FirefoxProfile profile = new FirefoxProfile();
profile.Port = 9966;
Global.Driver = new FirefoxDriver(profile);
P.S. I'm using firefox 16 to not have this issue
I have same issue with selenium version 2.37.xx with Firefox browser 42.0 After updating selenium version 2.48.2 issue is fixed
None of the previous answers clearly state that specific versions of Selenium WebDriver work with specific versions of Firefox. This SO question tells us that the Webdriver/Firefox compatibility matrix is here.
The other thing worth stating is that Firefox tends to update itself more-or-less automatically when new versions become available, depending on settings. Since Webdriver does not update itself automatically, this opens up the possibility that the Webdriver/Firefox compatibility will unexpectedly break and your test scripts will stop running when Firefox updates itself to a version that is not supported by your Webdriver version. I suspect that the answers above that instruct users to re-install Webdriver using Nuget simply pick up the newest Webdriver which works with the newest Firefox that just installed itself on your machine.
To prevent Firefox from upgrading itself, click on the menu button in Firefox (three horizontal bars, upper-right corner), choose "Options", choose "Advanced" on the left menu, choose the "Update" tab at the top and you'll see a set of radio buttons under "Firefox updates". Choose a setting other that "Automatically install updates".
I solved this by completely removing firefox and all profiles and reinstalling.
Error image
See the error image, I uninstalled completely and re-install version46, things solved.