iMac Core Duo: Vertical line distortion on screen

Several readers are reporting an issue where one or more vertical white lines appear on the iMac Core Duo's screen, distorting the image.

We previously reported a similar issue with the MacBook (13") -- that problem was apparently caused by the Mac OS X 10.4.7 update.

MacFixIt reader Gareth writes:

"Seems to be a big problem of Intel iMacs waking up from 'sleep' and having distorted images, vertical lines and refresh flickering for about 20-30 minutes after wake-up. I have contacted Apple where I bought the machine and they are claiming it doesn't exist on any other machine they have seen and are suggesting work environment."

In some cases, the vertical line distortion appears after a few hours of the computer being turned on but no operations occurring. In other cases, the vertical lines appear after the computer is woken from sleep.

This appears to be an issue with either video RAM or the Radeon X1600 graphics chipset included with Intel-based iMacs.

Some users have reported that holding the following keyboard command at startup temporarily resolves the issue: Command, Option, A and v.

If you are experiencing a similar problem, please let us know.

For more coverage, see our Intel-based iMac special report.

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