What's more mysterious is how Anakin goes from an American accent in the PT to having a RP English accent in ROTJ (even if you mess with the pitch of James Earl Jones's voice it sounds like an RP English accent).

Children can change accents with much more ease than adults so I can take Jake Lloyd speaking the way he does (though some of the words and actions make my stomach spin) but after growing up around Obi Wan I'd imagine he would have ended up sounding like Seb Shaw a lot sooner.

The only two incidents of adults doing it that I'm really aware of are Clive Barker (who now sounds like someone doing a bad impersonation of Louis Armstrong) and Rick McCallum both of which are originally from Liverpool. Maybe someone should approach Clive to redo the Jango voices for the PT.

It seems weird to me that people cling to the notion that Boba Fett's voice change in ESB:SE was a good idea and don't point out the more obvious and jarring voice change in a main character between the two trilogies.