(Windows 7 platform) On Eclipse with latest Selenium jars added to the Build Path, I wrote a simple Java application which only launches a website. When running the app, the latest Firefox for desktop 38.0.1 always showed an error screen with 2 options in it, and I had to click either one to proceed. However, after taking the trouble to downgrade to Firefox Desktop 37.0.1(or 37.0.2) the app now runs from beginning to end with no manual intervention and no errors.