updated 09:45 pm EST, Thu January 16, 2014
Problem possibly linked to bad solder, poor thermal paste application
As evidenced by a growing thread on the Apple Support Community, some early 2011 models of Apple's MacBook Pro line are continuing to suffer from a GPU overheating flaw, eventually requiring a motherboard replacement -- generally at the user's expense, unless the owner elected to purchase AppleCare. To date, Apple is treating each incident as an isolated event, despite numerous reports.
Machines afflicted with the GPU problem demonstrate display discoloration, and image distortion. Some users report random computer freezes with no graphical corruption. Rebooting doesn't generally fix the problem, nor does the Apple-recommended OS X reinstall.
When the 2011 MacBook pro was new, self-repair site iFixit noted that there were "gobs" and "absurd amounts" of thermal compound connecting the CPU, GPU, and heat sinks. The compound is intended to facilitate heat transfer between two surfaces, but excessive amounts can cause problems.
The iFixit teardown noted that the excess paste "may cause overheating issues down the road, but only time will tell." It is unknown what effect the paste has had over time, but thermal paste manufacturers note that excessive compound can actually inhibit proper heat transfer.
Other users have had success with third-party repair shops in re-flowing the solder connecting the GPU and CPU to the motherboard. A theory has been put forth on the message boards that a shift to lead-free solder is part of the problem, but as with the rest of the issue, Apple has no official comment on the matter.
The thread detailing the problem is now 157 pages. Some forum users have found a limited solution in forcing the computer to keep using the lower powered GPU onboard the processor, and disabling automatic switching to the AMD GPU. The vast majority of the complainants have been forced to have the logic board replaced in the afflicted laptop.