And it's still not possible - at least with Vbulletin - to use the filesytem for storing attachments when safe mode is enabled.
The problem is that VB creates several directories where the attachments get stored and when safe mode is enabled, the directories may be successfully created, but they can't be accessed.
A workaround would be to edit the PHP files that all attachments get stored in the same directory, without such a modification you'll need to use the Database as storage.