I was driving I-70 the other day, looked down and noticed that my speedometer showed well past 120MPH when I obviously was not going that fast. I pulled over, stopped the truck, and my 0 speed was shown as 90MPH. I turned off the key thinking that the system would reset, and when I turned it back on I seemed to gain back about 5MPH, so my 0 speed was now shown as 85MPH. Over the next few days it eventually got back to 0MPH through normal usage and it's been okay since. I recently when on a long trip that was about 90% cruise control and had no problems. Any ideas what the problem was and my chances of having this recur?