http://www.gamedev.net/topic/648431-putt-updates-and-finals-thread/?view=findpost&p=5103161

So this user has attached a download to his post. But when I click on it, I get an error from GDN telling me that I don't have permission to view the attachment. Am I, the user, or the site doing something wrong?

I get the same error so it's not you. Can't think of why the site would have a problem with it - if it wasn't an acceptable format the site shouldn't have let the user upload it in the first place...