After starting up a watermill the sound it makes will repeat, even after leaving the world (esc>save and quit).
Also after connecting a watermill to a batbox and then disconnecting them from each other, the batbox (with no connections made to it) will continue to charge at about 1EU per second (that is the rate at which my watermill is generating for me [5 source blocks of water are around it]). It stops charging after restarting the world, but the charge that was gained between the time of disconnection and exiting the world stays.
IC Version: Client 1.23
OS: Windows Vista
The world was generated with IC version 1.15, however both the batbox, watermill and wires were created and placed in version 1.23
Edit:
Also, after removing a watermill, the sound still continues. Also for the sound glitch to occur it has to be surrounded by water, not man feed.