Description of problem: Firefox saves temporary files for external apps to handle without an extension, and gnomevfs (and everything that uses that...) to mistakenly guess the mime type is application/octet-stream. How reproducible: Always. Steps to Reproduce: Go to <http://arxiv.org/abs/math.CO/0409509>, and click on the PDF link. Evince will pop up, and immediately complain that it does not know what to do with application/octet-stream
Firefox isn't the problem. The problem is that Evince has been lobotomized and requires GNOME VFS to identify the file type for it before it'll open it. GNOME VFS can't or won't identify PDF files without a .pdf extension, so they get the default type of application/octet-stream and Evince chokes on the file.
This is a dupe of bug #193582 and/or bug #186241. As comment #1 suggests, file magic isn't being recognised by gnome-vfs at all for *any* files (see bug #193582 comment #2).
Underlying cause appears to be: https://bugs.freedesktop.org/show_bug.cgi?id=6577
This seems to have been fixed in the last shared-mime-info update.
Fedora Core 5 is no longer supported, could you please reproduce this with the updated version of the currently supported distribution (Fedora Core 6, or Fedora 7, or Rawhide)? If this issue turns out to still be reproducible, please let us know in this bug report. If after a month's time we have not heard back from you, we will have to close this bug as CANTFIX. Setting status to NEEDINFO, and awaiting information from the reporter. Thanks in advance.
As I said a while ago,this got fixed by an update in the shared mime info db, AFAICS.