jPV wrote:
Check your screenmode settings in MorphOS Preferences -> Monitors, there's a list of available screenmodes and you can create new ones if something is missing. You can also test existing modes by selecting a mode and clicking the Edit button (or double-click a mode).

I think sqrxz uses 640x480 mode by default and Smokin' Guns 800x600, but I'm not sure about color depths, but check and test that you have those modes in all 8bit, 15/16bit, and 24bit depths.

Newer monitors may also not work with the lowest resolutions anymore, like 320x240, but maybe that's not the issue here...