The Toshiba Qosmio x305-Q705 with a NVIDIA 9700M GTS has had an issue with power consumption and overheating sense it was first released. My symptoms are quite worse than yours as mine will blackout with any browser and sometimes randomly. The only fix that I have been able to get to work is to use Rivatuner to modify the power compunction settings to stabilize the GPU. The only driver that I have been able to get it to work with is 186.42. It enables the Forceware that Rivatuner needs to modify the settings. It is a band-aid for the symptoms, not a fix, But it works.