Many thanks to all those that assisted my S.O.S message.
The problem was, as many of you suggested, the configuration word. I
have not still learned a lot of  the assembler, but my programmer
includes an utility to configure this word manually and after making it
the PIC  worked as wanted. At the beginning I thought that the Chip came
configured by defect to work with crystals now  know that i should not
suppose anything.

Well friends, again thank you. I will be working very hard to be able to
participate in an active way in the list.

Carlos Gruber.