Since 1.1.1 and continuing into the current 1.1.3, using Escape or the Enter key to select the attribute in the "Select Attribute" menu (Alt+A or Escape; "Select Attribute" from "Colors" menu) causes the program to close immediately afterward. This does not happen if you use the mouse to select an attribute.
Update: this program closure also occurs if you hit Enter to confirm the Canvas Size when changing it, or use Escape to close out of changing the Canvas Size or editing the Sauce Info. This, again, does not happen if you use the mouse for either of those things.
I am on Windows 10 and using the standalone application (instead of the Setup EXE).