An investigation by Apple shows some MacBook Pros may have faulty Nvidia graphics processors after all, despite Nvidia’s earlier assurances to the contrary, the computer maker has announced.

Apple said it will repair at no charge MacBook Pros where the Nvidia GPU has failed, or fails within two years from the purchase date. Problem signs include distorted or scrambled video, or no video on the screen though the computer is turned on. Models that might be affected are 15-inch and 17-inch MacBook Pros with Nvidia GeForce 8600M GT graphics processors. The computers were made between May 2007 and September 2008.