@mitu na all roms are running on the sd card, 32GB sandisk. I have a few of them that I cycle through during updates etc. All of them have shown the same behavior. I haven't changed default config.txt.
I'm using an LCD monitor with hdmi, not sure if that was the screen question :)
Also the map message only happens with Galaga so far, Berzerk does not show that it just completely freezes, screen does not go black like Galaga does.
@cloudlink I just figured it out. Hit TAB while the game is running then VIDEO. Change MODE to anything besides AUTO and the sharp pixels are back. It doesn't work as well for Advmame 1.4 but Advmame and Advmame 0.94 seem to do the trick.
@afscoelho you probably have the roms in the wrong place. Where exactly did you put them? check the documentation here for details. As @gaavoid mentioned, you can also use the arcade folder. AdvMAME (3.x) uses .106 romset (they go in the same place) and it is a better option than 1.4.