Is there any way you can add in a DEBUG after the "hserin 15,PasoSerie,[b0,b1,b2,b3]"?
Just to output the raw recieved bytes to monitor in a terminal.

The other thing that you could do is to clear the RX FIFO before enabling the reciever with "cren = 1". Something like

temp = RCREG ' clear first byte
temp = RCREG ' clear second byte
cren = 1