My T530 NVIDIA card goes slow

[Zniper]

After a day testing/playing Call of Duty: Black Ops using NVIDIA NVS 5400M card (it ran smoothly under 1600x900 resolution), the next morning, my machine became surprisingly slow without any changes made to the Windows 8. The fps of game now drops to less than 10fps.

I switched back to use the integrated video, everything seems normal with it. I switched back to NVIDIA and using some other benchmark tools like MSI Kombustor, or Unreal Engine, it stills shows the very poor performance (much worse than the integrated one).

I did update the BIOS, NVIDIA card driver,... to the latest ones, reinstall Windows,... but nothing changes.

Does anyone have any experience with similar issue on T series or the NVS 5400M specifically?

Thanks much,