Someone actually told me the real deja vu feeling (read: not the general one you get from PRing, but the feeling that what you're currently experiencing has definately happened before, detail by detail) is a "memory allocation" screwup.
Basically, he told me that he read that when you experience deja vu, instead of storing what's happening in your short term memory, your brain "goofs up" and stores it in your long term memory. This makes you feel that you're "remembering" what's currently happening as having happened a long time ago. You'll notice if you try to remember when it happened, you can never place it. "It just did."
Deja vu is also a glitch in the Matrix, or so I've been told 
-Ramon http://razor.ramon.com
