Alienware M14x: Temperature sensor not working on GPU

I'm having a rather unique problem with my laptop, specifically with the Nvidia video card (GT 555M). I have a feeling that the temperature sensor for the GPU is not functioning properly.

Whenever I run games and benchmarks, the temperature never records above 58 degrees. I know for sure that the Nvidia card because of the performance (ex. I got a P1454 on 3DMark 11, and it also says that the Nvidia card is in use). I have also tried the most intensive games, but no matter what I get similar maximum temperatures: 57/58C. I have looked around this and other forums to see what temperatures other people had, and all of them (including those that apparently went as far as repasting the thermal compound) had temperatures around 10 degrees higher than mines.

My suspicion is that the GPU is actually reaching very high temperatures, but since the temperature sensor is not working properly the recordings are not correct. This is a problem because the fans never kick in to the higher speeds to cool it down. I have no idea how long it's been like this, but I fear that the longevity of the GPU has been compromised in some way.

There are other symptoms I've seen. In TES V: Skyrim, for example, I get random FPS slowdowns every 10 or 20 seconds that each last about 5 seconds. I know that the Nvidia card is more than capable of running the settings because other than the random slowdowns I get smooth gameplay. Another symptom I've seen are graphic artifacts in 3DMark 11 during the last combined CPU/GPU test.

I've already tried software solutions such as reinstalling the Nvidia drivers (tried both 285.62 and 290.36 beta drivers), and I'm pretty much convinced that this is a hardware problem.

The fan doesn't have any problems either, as the high speeds kick in fine when the CPU is reaching high temperatures during the CPU benchmark in 3DMark 11.