I've been trying to re-download The Witcher since this morning, and the game was downloading fine until it got to about 98% and then the download stopped. I've restarted the downloader a few times since then, and also tried to remove the game from the list and re-add, and each time it now complains that it can't retrieve the game info. To check to see whether it was an issue with the download system or just an issue with that particular game I also tried adding Thief Gold, and it appears to have the same issue.

Are there any known issues or is anybody else having similar problems?

NOTE: Technically the solution is more of a Workaround than a solution for the original downloader, but it did the job so it's worth a try for anybody who's experiencing the same problem.

I've turned Windows Firewall off completely as it's useless on this computer, however I doubt it would be a firewall issue anyway as it was downloading fine up until a certain time. As this is a fresh install of Windows I grabbed the latest Downloader available through the link provided on the popup box (when you first add a game to the downloader), so I assume that's the same as the one provided in your link? If not I'll give that a try.

I don't think it is the same. As the one I linked is still in beta. Worth a try I guess...

It seems it isn't the same downloader, so I gave it a try, and it seems to have fixed the problem. Annoyingly it won't pick up the files already downloaded with the previous downloader though so I have to re-download the entire 8.4gigs :(, but that's just a minor nuisance.