says that some of the AMD Radeon HD 6970M graphics cards used in 27-inch iMac
systems with 3.1GHz quad-core Intel Core i5 or 3.4GHz quad-core Intel Core i7 processors could fail, causing the display to appear distorted, white. or blue with vertical lines, or turn to black. Systems outfitted with a potentially affected GPU were sold between May 2011 and October 2012.
There's now a replacement program in place, so if you own an iMac with Radeon HD 6970M graphics that's exhibiting any of the above mentioned symptoms, you can have it evaluated at an Apple Retail Store or contact the company's Technical Support for local service options.
"If the iMac (27-inch) meets these requirements, Apple will replace the video card free of charge for three years after the first retail sale of the computer," Apple said.
Some iMac owners can't seem to catch a break. Prior to the GPU replacement program, Apple offered to replace faulty 1TB Seagate hard drives used in 21.5-inch and 27-inch iMac systems sold between October 2009 and July 2011.