Hi Louis,
I think you are correct and perhaps I should have mentioned layouts. In normal operation, MaLa displays Mame games absolutely fine, its the "layout" that looks wrong.
With no layout skin, there's a short list of games which overlay my game snaps (making the text almost unreadable). I have grabbed a couple of 3rd party layouts which include vertical options but of course, only display correctly if I tell MaLa to rotate my display.
So my next question is... is there a way to get the layouts to switch to match the "native" vertical screen?