The issue is resolved now. djensen has informed me, that he freed up some space.
I have already tested it, and new savegames will be uploaded to the forum correctly as well as downloaded to the user’s harddrive.
If you guys wouldn’t mind, please move comments to the new thread. I’m not going to close this one because if you want to quote somebody else’s response and paste it into the new threads, I would like you to do that.