Mister_e,

You were right: LPV must be switched off to make it work.

As specified in the 16F88 data-sheet (chap 15-18), if LVP is selected, RB3 ceases to be a general purpose I/O pin. As I used this port in both tries (PortA and PortB), it coudln't work.

In a few words, here is what happened to me:
a.- three LCD displays not HD44780 compatible (even Murphy wouldn't have so much bad luck);
b.- LVP switched on by default in ICPROG (my programming software).

Thank you all for your support ...and patience.

Hope this thread will help other people too.