I posted this in R & N but it was deleted???
Anyway, some years ago whilst operating an A340-300 in the Far East we flew into some light cloud at night with no turbulence. All of a sudden the Capt's IAS dropped to around 120kts whilst the F/O's & stand by continued to show reasonable indications. At the same time the TAT & SAT indications increased to something around -20 c at cruise FL(can't remember exactly but must be FL330+). Since an we were already aware of the problem(we had been issued an incident report rgarding a Cathay A330) we weren't in too much shock. Airbus' write up about the problem was that the heating in the TAT probes,at times, may be insufficient & lead to the probe icing up followed by the ice rapidly heating up giving false TAT & SAT indications.