Possibly your video card is projecting the screen too high up or too long to fit in the viewable area? The scores are at the VERY top of the screen. Do you see a high score at the top in the middle? Should look like this...Originally Posted by DragonMaster Sam
(from klov.com - now if they'd finally post my damn SCUD Race marquee picture)
If you don't see "1P [YOUR SCORE] HI [75800 IS DEFAULT]" at the top then you need to change the screen size, most easily by using the manual controls on the front of your monitor. Scale the vertical size down a bit and the missing score line should come into view.
If you are just getting started with MAME this can sometimes be a problem with vertical games until you get some of their resolutions centered to where your display shows them properly.