I have now received emails from Celemony support indicating that IE9 is required, (or Safari browser).
I don't think they meant this as a requirement. They probably just suggested to try a different browser to see if this is the problem.
I can't remember anyone else having troubles in the past when downloading Melodyne with IE 7 or 8. So I would not say this is a general incompatibility issue. By the way, have you tried another download since? It might as well just have been some temporary server hick-up.