more importantly did it restart and go back to normal?
Yes. I restarted and it's back to normal. But is this a sign of more bad to come?
Late 2008 edition.
256MB or 512MB GPU? Maybe your GPU is failing. If it is still running, then it should be fine. Just keep an eye on it and if it happens again, thats when you should get concerned and call AppleCare.
Could be a graphics card problem. Try installing the latest drivers.
2. It's a mac remember? 🙄
I think this is a sign that you have not restarted/shutdown your machine for some time, am I right?