Anyone else get image persistence on their 24" iMac with Radeon 4850? I sometimes work on the system for up to three hours in a row, and after I'm done I notice lines, shapes, and text "burned" into the screen. I have screen power down enabled where it turns the screen off in about 5 minutes when I step away from the computer, and usually turn it off for the night. This helps revert the screen back to being clean, but once I use it again for several hours non-stop, the shapes come back (from different applications). I've noticed that this happens whenever the system heats up slightly (due to hard drive working, or graphics, or cpu getting warmer compared to idle state). Here's a screenshot from iStat where I have several Adobe apps, and FireFox loaded: Anyone else experience anything similar? I know it's not that big of a deal since it doesn't remain permanentl, but I'm just wondering if it's something to worry about. I've had the system since it first launched last summer, and as far as I can remember I've had the same thing happening throughout this time, no matter what my room temperature has been.