I also have had problems with serial LCD coms. I have tried serial modules form 4 different manufacturers and have spent hours trying to make the buggers work. Well, NO MORE!!!
In utter frustration, I tried the setup exactly as listed in the MEL manual for connecting to an LCD direct. First time success. I know there is a lot of talk about the extra lines required, but, is it cheaper to move up 1 size in PIC for a cuppla bucks, or add a serial adaptor for a cuppla bucke. No arguement. I will be using the book's example from here on in. It really is so simple.