I think that if you open a window (any window)...grab the window by the title bar...and move that window around the display over all the "funky" image...it should disappear.
As to the cause. If it's not a hardware issue (software issue)...my guess would be that there's some sort of:
- App to OS conflict/confusion.
- App to app conflict/confusion (2 apps not "playing nice" with each other).
- Computer needs some maintenance (run the free maintenance app called "Onyx").
I would also mention that occasionally rebooting the computer can be helpful. I know you mentioned not liking to reboot the computer because it takes some time. But if this reboot is done when you will be busy with non-computer things...then no biggie.
I would say once/week...maybe once every 2 weeks...and see if this helps. Many folks go longer than this. But since you are having an issue...maybe doing this will help.
- Nick