Minecraft flickering and entities flashing out of existence

I start up minecraft in either 1.6.1 or 1.6.2 and click on any button. This causes the top of the screen to start to flicker and glitch. The longer I keep mine craft open the worse the flickering becomes, until all buttons on the menu are replaced with weird white flickering text that is unreadable. If you start in a world (either a server or single player) the flickering continues until the game is unplayable. All entities are affected as they seem to flash in and out of existence in the minecraft world. Changing the settings does not help and im not using a resource pack. This glitch appeared after downloading the newest version of Adobe Flash Player.