About the i.rectify problems...
Are you sure that the region you define in the target location is big enough
to fit the whole rectified image? When the image is rectified it will have
some rotation and maybe the region you defined is not big enough to fit
this rectified image. When you give the UTM coordinates in the region of the
target location you should give coordinates that contain more than your
original image.
Hope this helps!
Cristina Seabra
cis@fct.unl.pt