I figured what was wrong with exporting grass to postgis:
The error
ERROR 1: AddGeometryColumn failed for layer mamma, layer creation has
failed. ERROR: Cannot create layer
come up because I had a database and a schema with the SAME name!! Bad idea, I know.
I changed the schema name (ALTER schema <name> RENAME <new name>) in postgresql 7.4.1 and everything worked fine. It defaults to the schema "public"
I wonder if there is a way to specify a schema in v.out.ogr?!
Thanks for the help
Francesco Pirotti