So I bought this game a while ago, expecting to use it once I upgraded to a proper computer from my shitty old laptop. For some reason, though, I cannot get this game to download off of the Galaxy client (and, having just thought of it, I tried the old fashioned way and that's borked as well). The game will be stuck in the 'collecting file list' stage of spinning progress bars for 15 minutes before it switches to an error message of some kind (I didn't think to catch which error it was, I was too mad and immediately tried to restart the download). I tested whether it was my internet connection or the client by downloading other games through it, and they went through absolutely fine. It's only Jade Empire that's stuck in this infuriating stage indefinitely. What the hell? Is there some kind of server-side issue that prevents me from even downloading this game I paid for?

Although I can't say what causes the problem, there are some game that have this problem... Usually big games, for my knowledge. JE is one of them. For me it's usually disc access problem after moving. I would recommend doing report post on http://mantis.gog.com/ and/or go to GOG Tech. Support.
Also - where are your games installed? In the default folder inside Galaxy client? If so, I would recommend creating outside folder for the games. And... I pressume you tried manual download the instaler via Galaxy for "Extras"?