This just started happening today. I have a 2009 iMac running Snow Leopard. When I click on a file that is MOV (or any file for that matter), I try to type in .MKV or .MP4 and nothing happens. It just resorts back to it's original file type. This is bad because now I can't use HandBrake anymore as the files will not go through it. Is there a glitch in my system? This is the first time I've ever had this happen.