Someone had posted something like this before (looseing power steering at speed...120 or so). I'm not sure if anyone came up with an answer. I had this happen to me. I had it up around 120 in 4th and just want to coast into an exit. So I disengaged the clutch (I'm not sure if I shifted into neutral) and the power steering faded away and made it tough to steer. I reengaged the clutch in 4th gear and the power steering came back about as fast as it had faded away. Seems like the sensors for the power steering are a little quirky!