The 'P' bar is usually to do with the memory sliders in the graphics options. I can't remember exactly, but I have the GPU slider slightly lower than the amount of GPU Ram I have, then it's all about playing with the RAM slider. I have mine set to 1200, even though I have 4GB. My P bar almost never goes into the colours and is usually empty, you just have to fine tune the memory sliders. It all depends on how much RAM you have, but keep lowering it until the P bar shows only grey. That could also explain the skipping.