I recently took apart my very out-of-warranty late 2011 Macbook pro to clean it out and replace the thermal paste (it was starting to sound like a plane when I played stuff on Steam). This was an apparent success because combined with cleaning out the fans (where there was a LOT of fluff), the temperatures have dropped fairly dramatically. However, the GPU diode in iStat Pro on the dashboard are now reading a very low number (anywhere between 1-20C) or going into negative numbers like -127-128C. This is only for the Intel 3000 GPU. The discrete graphics card reads around the same temp as the GPU itself and appears to be fine. Can anyone explain what caused this? I've taken it apart before and not had this issue?