the carrier movement is normal - they all do that BUT the fact that you can hear it above all the din the bike makes is not normal.
I would say that you have rear caliper problems - its sticking - once "unstuck" there should be no noise - if you can - try removing the rear brake COMPLETELY FROM THE BIKE and see if the noise is still there.
Caliper needs cleaning/servicing/binning etc
Khushy
[Edited on 12-5-2006 by khushy]