Something very similar happened to mine on a rolling road, it then did the same with a coil and melted it. I have had other minor issues of gauges/sensors freezing with a laptop connected i.e. MAT, TPS etc... resolved by restarting the car or Vemstune.
It's with Rob at the moment for diagnostics, so will hopefully know more after the weekend.
Mine is a V3.3 running 1.1.98, what is yours?
Alex