Vertical games cannot have authentic resolutions set for them on horizontal monitors when rotated. You are trying to force 288 line modes on a 240 line display, which means you will lose line information.
Visual explanation here:
http://advancemame.sourceforge.net/blit.htmlYour choices are:
a) Accept the limitations
b) Use a blitter/stretch mode (eg: Use 640x480 with ddraw stretch)
c) Use something like AdvanceMAME which compensates for such problems with the above linked blitters
d) Play your vertical games on a separate vertical display.
e) Make your cabinet's monitor rotatable
