Getting a blue screen

I have no idea where to post this so I just picked somewhere since there isn't really a "general" help area.

I've had this computer for about 2 or 3 years now. I use it primarily for digital drawing since I'm an artist and it's how I make my money.

TWICE today I've gotten a random blue screen and my computer shuts down. I have no idea what it means and I really can't afford obnoxious setbacks like this.
The blue screen is completely random and does not happen when I start it up. It did this about a year ago, but has never done it since today.

I need help figuring out the problem so I can get back to my work without worrying about loosing the files I'm working on.

Info:
Version 10.5.8
Processor: 2.8 GHz Intel Core 2 Duo
Memory: 2 GB 800 MHz DDR2 SDRAM

Post the kernel panic log so we can have a look at it and possibly narrow down what's causing the panics.

Click on the "Apple" in upper left of your screen, select "About This Mac". Then select "more info". Scroll on down to the logs entry, highlight "logs". On the right side of the dialog look for the panic log. Then copy it to your clipboard and paste it in your reply to this thread.