I agree with what Erik said. You should make sure that EXTRAM bit is set before addressing your memory mapped LCD drive. As to the activities on P0 and P2 you mentioned, were you observing all these while running an in-circuit emulator? You may want to check emulator's manual for a proper configuration that suits your application.

In my first response to your original message, I asked you if you had tried to "access your display with setb/clr on A15 and A11 instead of using "movx" as a memory mapped device". What I meant to say is that since you only need A15 and A11 as two control lines (i.e. CS and C/D) and RD/WR strobes, you can "simulate" the read/write processes without using "movx" instruction (you'll need pull-ups on P0 in this case). This will not work as efficient as "movx", but at least you'll have a total control of everything.