I think this relates to general mame, but I am using groovymame so I thought I should still post here.
I was playing Metal Slug 3 when I went through the tab menu -> video options and selected Marquee only.  The screen went completely black and now I can not even get the tab menu to appear when restarting the rom. 
I can not find an ini, cfg in my folders for MS3 and I tried deleting the nvram. Any idea how I can fix this? 
Thanks for any help