I'm using one of these as it has a (Duo compatible?) display connector, SD card, full debug connector and all the pins are brought out - it makes a good development platform.
Looks like it was a timing issue, the 9486 LCD is a Mega style shield (although I don't recognise the pinouts as being anything like a Mega) and hence has very short connections. The 9488 is a bare LCD with a FPC on the end of 200mm of patch wires.
All sorted now 