When you change your aspect ratio (PAR), the pixels change shape. This can create a blur, stretch or other problems when you are starting with square pixels and then changing them. Also remember you are downconverting. What you want to do first is downconvert to a squarepixel variant of the resolution. The pixels are rectangular in a 1.46 par. So your height would be 1, your width would be 1.46. Multiply 720 by 1.46. That's 1052. So now you are 1052x576. You see? Your Par didn't convert down, you blew it up in an odd way. You want to convert to a new PAR, find out the exact size of your video at a specific par. 1050\1.46 is just over 719... ...You want to use the 719 value, not 720. You'll need a custom size. Now, set up a sequence for 719x576, place your video. Set up another sequence for 720 if you want, and place the 719 into it, then scale to frame size. You won't have any more problem.