TMZ has been approached by someone attempting to sell a sex tape of Usher and his ex-wife Tameka Foster.  Here's the scoop:Usher's reps aren't commenting, but sources are saying that the video may well have been stolen from his car back in 2009 - when he reported about a million dollars worth of jewelry and electronics were taken.  When are celebrities going to learn that filming themselves doing the deed never ends well?  And who the hell carries a million bucks worth of jewelry and personal videos around in their car?