My guess: You click the link which launches windows media player. It fails to download.
Reason: WMP can't download the >= 2 gig files from archive because the Content-length returned by them is negative. That's a problem of course, but a browser will still download the file correctly, just with "unknown" size. So... use 'save as'.
Actually no. I haven't downloaded anything that big come to think of it. The normal quality version is downloading fine. That's an interesting point you make; I never thought of that. Is there any way I could get the HQ?