I don't remember when this issue resolved itself. I was running Snow Leopard at the time. I have since moved to Mountain Lion OSX10.8.3 today. I moved to Mountain Lion a couple of months ago. Today, I can drag and drop any movie, whether HD or not and play on my Quicktime App in my Dock. So the issue has resolved itself in either SL or ML, but when and why I do not remember. Sorry.