The error issued by d.mon:
"can not allocate any read/write color cells"
was solved by including the line
exec X :0 -bpp 32 $*
as stated in www.geog.uni-hannover.de/grass/admin/allocate_colorcell.html
Thank you all!
Dr. Agustin Lobo
Instituto de Ciencias de la Tierra (CSIC)
Lluis Sole Sabaris s/n
08028 Barcelona SPAIN
tel 34 93409 5410
fax 34 93411 0012
alobo@ija.csic.es
http://pangea.ija.csic.es/alobo