ah, r.basin is just a python script. http://trac.osgeo.org/grass/browser/grass-addons/raster/r.basin/ try to download r.basin.py and stick it in /usr/lib/grass64/scripts/: sudo svn export https://svn.osgeo.org/grass/grass-addons/raster/r.basin/r.basin.py /usr/lib/grass64/scripts/r.basin then see if it works... Hamish