I turn off Auto ISO on a D7000 when I'm using the flash.
Wasn't a problem on the D300 or D80, and may have reverted back in newer models.
I find it most useful when doing macro photography, so I usually turn it off when I attach my macro lens.
It will reduce un-necessary noise in your photos.
This was the only change I didn't like in the D7000.
It can be added to the U1 or U2 function.