Recently Selenium Webdriver upgraded from version 2.41 to 2.42. Unfortunately with the change a bug was introduced. On OSX machines using a Retina display – the browser would load with uber tiny fonts. Barely legible. Many actions still worked, some would not.
In my case I had some tests that require image recognition, so my tests would fail with the tiny new minimized graphics and text. The solution was to downgrade your selenium web driver to 2.40.0.
However recently I noticed after a reboot that I was having problems again with this. My code was definitely setting selenium web driver to 2.40.0, yet I was still having this problem again.
It turns out that I still had the selenium 2.42.0 web driver installed on the OS. Since I use Ruby via RVM, RVM installs gems specific to each Ruby installation. When I went to my home directory/.rvm/[ruby version]/gems… sure enough the selenium-webdriver-2.42 was there. After deletion, everything came back to normal.