I have no idea what any of yous guys are talking 'bout - my SB400 operates as iTTL and manual from full power down to 1/128th or summat.
This might seem like a matter of pedantic semantics, but it isn't. I intend no offense.
The SB-400 does not have manual power adjustments in the traditional sense. It is truly i-TTL only. Without the circuitry of an i-TTL body the SB-400 can not be operated at all. Place it on a D100 even, and it is a paperweight. Your body allows manual power adjustments from full to 1/128th. Not the flash. It has no external controls, no external trigger port, no trigger switch, and will not respond to the historical precedent of grounding the trigger pin.
Any flash Nikon sold prior to the SB-400 could be operated manually. A paperclip was all that was needed (if one were so inclined) to fire the flash at the power level of ones choosing.
I make this point because it is precisely this imprecision in language which leads to the confusion expressed by the thread starter.