I found a strange bug, which totally locks up my computer and forces me to restart it. I'm using Snes9x 1.53 on Mac OSX 10.10
The following course of actions are needed:
Prerequisite: Use a USB joypad and fullscreen is probably nescessary.
1. While inputting a command (such as the D-pad) disconnect the joystick. My usb-port is a little bad, so this happens from time to time. This causes the command to stick.
2. Perform a Freeze or Defrost. Now the selection will be scrolling by itself and the computer wont respond to anything (I cannot use cmd+Q to quit snes9x). I had to push the power button for a few seconds and restart the computer.
It might not be the fault of Snes9x, but rather the USB joypad driver. Anyway, it should not lock up like that.