To all those having problems with QTA 2.X., here's the solution: update your graphics drivers - if possible, to the latest versions. I have just done so. And now I can download & watch any qt based clip, without the phenomenon of "browser blocking". (For example, if you have installed NVIDIA Forceware 94.24 WHQL drivers, as I did, please update them to NVIDIA Forceware 185.85 WHQL version. This can also solve some Media Player blockages!)
Unfortunately, this version of QTA is not working as fine as the previous ones. I think that the developers were in a big rush, if they delivered it without testing it enough. Yes, the enclosed download tool is still usable: you can use it to download, and then, to watch HD clips, either in your default browser, either with your favourite Media player. But I encountered unexplainable problems, with QTA, when I visited the website belonging to Apple Computer. Here's the URL: http://www.apple.com/trailers/. When I tried to watch some trailers, my browser has BLOCKED itself. In fact, with all the usual browsers I have had the same problem. Finally, QTA allowed me to see some clips. But not all of them. I do not know the "internal criterion" after which QTA guides itself, in rejecting/accepting to render certain movies. All the QTA settings were those provided by the default install. I do not know why this version has such a behavior. Maybe the guilt (the bugs) belongs to Apple.