Did you also have your foot on the brake whilst going down hill? The reason I ask this is that a couple of weeks ago I took my X out at night, got about a mile down the road and my dash came up with the same lights as you quoted. I also noticed that my brake lights were staying on... After investigating I realised that earlier that day my two young sons were in my car whilst I washed it,one of them must have kicked the switch unit above the brake pedal which made the brake lights stay on. This I can only think confused the car as I was driving it, thinking I also wanted to brake which resulted in the above.
I reset the switch as its on a ratched type thing and all has been well since...
Dweeb