In the game's ini file (ie zookeep.ini) set:
resolution 640x480
(or whatever resolution your game supports). Doesn't that monitor only support one resolution anyway? If so, you may want to add that line to the main mame.ini to set it for all games.
Get rid of the AUTO resolutions and add the switchres 1 line...
The exact message I'm getting is:Out of Range
Hf: 30Khz - 38Khz
Vf: 40hz - 150hz
86hz / 43.3hz
my zookeep3.ini file only has the one line in it: "resolution 640x480" (this does not fix the issue)
I'm going to change it to:
resolution0 640x480
switchres 1
and not touch the mame.ini file. I'll report back!