Hi Shack (and all),
Even if you are a new member (with some moderated posts at the beginning - sorry for that but we need this against spammers), you should be able to access attachments with no issues when you are logged in.
Make sure that you have cookies enabled and if the problem persists, try to delete your sketchucation related cookies in your browser (and for God's sake, do NOTuse Internet Explorer as it is a nightmare to get rid of cookies there...)