Black bars on iMac? (Late 2006)

Hi,

I've been getting weird black bars on my iMac. They seem to appear when there are alot of applications loaded. Some times they're on the side of windows. Sometimes on text. Sometimes my mouse turns green. Sometimes my dock is discolored completely. Take a look: http://imgur.com/RqpVOGY,UgOIlLA,ImwHxHg,ioGfArs

It's just plain annoying, really. 🙂 Anyone out there know what it could be? I did a Apple Store chat (not knowing they wouldn't know) and they directed me to Tech Support, but warranty is out on my Mac so I'd have to pay $19.00 to find out. :/

Specs of my iMac:

OS X Lion (10.7.5)

iMac Late 2006

20.1-inch (1680 x 1050)

Graphics: ATI Radeon X1600 128 MB

Processor: 2.16 GHz Intel Core 2 Duo

Memory: 4 GB 667 MHz DDR2 SDRAM

Thanks!

Jojo