I use an iMac G5 (second gen, I think), OSX 10.4.11. All of a sudden, the pointer icon has a square of black ticks, the pointer icon in the top left corner. The dock is covered by black pixels, and any icons not affected, as soon as I click on them, they also have black dots. The finder menu bar is "infected" the same.

Anywhere where there isn't an icon on the background desktop image is unaffected. Some Save as... boxes (Grap app, for instance) are affected, covered with black ticks or dots. Quicktime videos look terrible, covered with these black ticks and/or dots.
I've done a total reinstall of OSX 10.4.11, zapped the PRAM, googled for viruses, or if this is a known problem without success. I'm really hoping it's a System file corruption problem and not any video-connected hardware stuff... (the fact that despite the still corrupted pointer/insertion icon wandering over Safari, all web pages are fine, gives me hope that it's the former...)
I'm a bit reticent (as well as trying to be an educated guesser only) when it comes to the System Folder, so I think it's best I follow someone's advice who knows what they're talking about...
Does anyone know how to solve this please?
