I'm unsure if this has been reported before:
While activating a fence gate with a torch in your hand, the fence gate is activated, quickly deactivated, and then the torch is placed on the side the gate you're standing on.
Then, you are able to continue to right-click the gate. This will cause the gate to activate and deactivate in rapid succession.
Unable to reproduce. The fence gate activates/deactivates if clicked, but no torch is placed. Unless you hold right click, the gate only switches once. Also, your Java version is out of date. Please update your Java to the latest version: http://www.java.com/en/download/. Keep in mind that when using a 32-bit browser on a 64-bit OS the automatic version detection will only show the 32-bit version of Java, the 64-bit version needs to be downloaded manually: http://www.java.com/en/download/manual.jsp.
Please report if the issue persists with the latest Java version.