That might be true, but let's hope for the best. There certainly was a problem becouse it was stuttering a lot. I don't think Fraps FPS counter lied. It was stuttering so much that I could not control the aircrafts and I crashed into the terrain. That last part actually happened several times.
Now, after reverting to 13.4, everything is fine.
I have no idea if it was related to that thing you mentioned about the card not using the right clocks. I should have checked before reverting the driver.