I've just attached a file to bug 27211 (twice - once using lynx and once using Mozilla; the result was about the same) and it turned out that when I try to view the attachment, I only see its name, not the actual contents! I was attaching a plain text .txt file using the "auto-decect type" option (which correctly detected text/plain). Since I can view older attachments fine, it would seem that it is uploading that is broken, not viewing.
Thanks. This should be fixed now. Previously failed attachments should be re-attached with others obsoleted.
Created attachment 88713 [details] Testing attachments (from Mozilla)
Created attachment 88714 [details] Testing (attaching from lynx).