Due to some peculiarities caused by installing Service Pack 2 on Vista I had to make myself a new user in safe mode of my old one (the old one wouldn't login normally for some reason).
When I checked the game explorer I noticed that apart from the Ishar pack (Which happens to be the last thing I downloaded and installed), every GoG icon was blank, and didn't point to any game.
I reckon there's not much that can be done about it (apart from reinstalling the games, or something of the like), but I thought I'd just give you all a heads up.
Whether it was the new user or the Service Pack that did it, I've got no idea of.

My guess would be that it's the user. See this post of mine, for an explanation of where that data is located. You might be able to simply copy the folders into your new user file structure.

Thanks, but I can find no such error as described in that post. All the entries have a single curly bracket at the start and end, as supposed to. Though it's probably tied to the user as you say. I reckon I could try to copy all the entries from the old user's appdata folder, and see if that might help.

That's what I meant. Not that you had the same problem. Just that that post showed you where the data for the game launcher folder was located.