If you are overclocking the GPU, it can sometimes cause issues with gaming and produce exactly what you described in your first post. Also, is it every single game and does it affect other applications? Also, ensure you disabled onboard graphics in your latest BIOS if the option is there. My last comment is that your new BIOS control may have changed the way the GPU fans are cooling. If that is insufficient then it could cause overheating the card which may produce the results you are seeing. Suggest you re-evaluate your fan control with the new BIOS.