I have a problem with my dock, every time I'm using my mac out of nowhere the glass portion of the dock will just disappear, and then when I open one of my stacks all the icons and text are completely gone. Then I have to restart my computer for everything to go back to normal. Real annoying. Is there anyway to fix this without restarting my mac, or to prevent it entirely. I've tried using the 'killall dock' command in the terminal but that doesn't do anything, I even tried resetting the PRAM and still nothing.