iMac keeps crashing - Adobe CS4 is running + Leopard OS

ARRRGHHHH! I feel like I'm using a Windows PC at work

I'm on a Mac OS X, version 10.6.3. Processor 2.66 Ghz Intel Core 2 Duo. Memory: 2 GB 800 MHz DDR2 SDRAM.

I'm a graphic designer so I always have Photoshop CS4 & InDesign CS4 running simultaneously 8 hours a day. (Firefox 3.6.3 is also running).

Never had a problem until recently - the screen would suddenly turn WHITE, or BLUE w/ VERTICAL STRIPES. Then I have to reboot.

I had 3 crashes today.

I did notice when I was scrolling w/ my (sorta old & ghetto Kensington mouse) that it froze the iMac twice.

IS THERE A PATCH, OR SOFTWARE UPDATE FOR THIS? Anyone else having similar crashes?