Hmm.. maybe you have set some permissions specific for the user. Tr y that: go to Admin Panel -> Users, and search for the user who is not seeing the download link, then click "Permissions" and set it's permissions there. See if it works now.
Maybe it work for one reason: once you set permissions for a specific user, the roles which will make effect will be only the ones you set for the user in this case, and not the group ones. In other words, if an user has specific permissions, JForum will ignore the group permissions for that user.
So, if you changed the user permissions sometime ago, and there the download stuff is disabled, that would explain why chaning the group permissions is not affecting the user's one now.
Rafael [originally posted on jforum.net by Rafael Steil]