Can program on pic family but not the other

I have sucessfully programmed the 16F688 but when I tried the 18LF4431 it
does not work. I read both specs and they seem to be the exact same(ICSP?)
and I have hooked them up right(pin wise) but when I use winprog to program
the 4431 it always fails(and I did select the right pic in winprog).

Only thing that has changed is that instead of 5.06V rail for the clock and
data lines they dropped to 2.3V or something like that. (But I think this is
in the limit for the LF?)

Only other thing that I can think of has to do with setting the clock in
winpic. Its set at LP but has many other settings... but not sure if this
matters when programming as it uses the clock of the parallel port.

I also have tried to delay up to 150us in winprog on the timing but it did
not work.

Any ideas? I figured the programming method would be the exact same(Except
for pin layout) but something isn't working ;/

Thanks,
Jon

 

Come on guys!! Can anyone think of a reason why a programmer would work for
the 16F688 and not the 18F4431? As far as I can tell the method is exactly
the same as outlined in the memory specifications of each document(aside
from the communications which is handled by winpic). I'm using Byron's
method by using a tri-state HCT device to buffer the lines between the pic
and the parallel port. I have tried all different settings in WinPic but
nothing helps...

The pin connections are the exact same except for a rearrangement and having
to ground the LVP pin... unless I'm missing something? Do I also need to
ground all the other pins or the AVDD/AVSS too?

(maybe there is something wrong with Winpic though? ;/)

Thanks,
Jon