I just tried Ctrl-q to no avail. I know my keyboard works as the tab, esc, etc. keys work fine under MAME. I also tried SELECT+START which are mapped to two keys on my controller.

Any other ideas? I think if someone can guide or explain where the key mapping file is for Stella I could maybe edit that file and get escape and tab enabled again. Escape is supposed to leave the game and tab would take you to the Stella control menu.