An Apple Knowledge Base Article describes the issue:
"In July 2008, NVIDIA publicly acknowledged a higher than normal failure rate for some of their graphics processors due to a packaging defect. At that same time, NVIDIA assured Apple that Mac computers with these graphics processors were not affected. However, after an Apple-led investigation, Apple has determined that some MacBook Pro computers with the NVIDIA GeForce 8600M GT graphics processor may be affected. If the NVIDIA graphics processor in your MacBook Pro has failed, or fails within three years of the original date of purchase, a repair will be done free of charge, even if your MacBook Pro is out of warranty."Symptoms users have when experiencing these graphics-related issues are:
1. Distorted or scrambled video on their screens.Resolution
2. No video on their screen (or external display) even when the computer in turned on.
Apple offers direction on what to do if you are experiencing this issue:
"If your MacBook Pro is exhibiting any of the symptoms listed above, please take it to an Apple Retail Store or an Apple Authorized Service Provider (AASP) for evaluation, or call your local Apple Contact Center. Before visiting the Genius Bar at the Apple Retail Store, please make a reservation.Note: If your MacBook Pro is not experiencing any of these symptoms, you do not need to contact Apple. Apple will continue to evaluate the repair data and will provide further repair extensions as needed.
Apple is issuing refunds to customers who may have paid for repairs related to this issue. Please contact Apple for details on the refund process."
Read the Apple KB article defining the issues with NVIDIA's GeForce 8600M GT graphics processors in MacBook Pros.
Read this AppleInsider article about Apple extending the warranties on MacBook Pros using the NVIDIA GeForce 8600M GT graphics processors.