Noticed the other night the screen 'flickering' between the screen saver and the desk top. I found this example on youtube:
YouTube - POWERBOOK, MACBOOK, MACBOOK PRO FLASHING SCREEN SAVER
The link shows a power book pro - but it is the exact same thing that my iMac was doing.
When It happened to my system, no program was running, I had walked away and it was the screen saver that timed on.
Anyone have any idea as to what the problem is? I also sounded like the system was working harder.
iMac 2.4, 20"
NO 3rd party screen savers installed