If i try download "Rayman Forever" i always get an Error. I tried on Website and Galaxy-Client. Is eventually the File at GOG corrupted?
I know sometimes the Antivirus block the download with a false positive but my Avast don´t say anything so I don´t think this is the reason.

It works fine for me. Maybe you should contact their support or try a different browser?

I have the same problem. I bought the game yesterday, and when the downloading is at 100%, a Windows message appears saying that the file is corrupted and it has to be deleted.
The message says (well, in spanish): "La firma de este programa está dañada o no es válida"

Edit: Download works on Firefox. The problem is on Internet Explorer.

I tried it with Internet Explorer(64Bit) and Firefox. Firefox is my regular Browser. It doesn´t work with either of it. The download stood still for a few seconds at the last part of the download and then it tell me the download isn´t complete. In Galaxy it says Serverproblems or Harddiskproblem. My hdd can´t be the Problem because i tried to download to different disks on my computer.

My Antivirus (Avast) was the source of the problem. It blocked the download but don´t tell me like i set in the option. I found in the virus container many blocks from gog-related things but Avast never told me something. Now i block the whole folder i use for galaxy and my games and voila: it works!
Hope it helps someone out there.

The level editor is detected as a false-positive by some antiviruses, just disable your antivirus while installing(Or while running the level editor).

Same problem here.