CHT thermocouples are pretty resilient.  The wire to them, however, is not.  Double check all connections, look at the routing--is it possible it's coming into contact with something hot?--look for kinks, breaks in insulation, chafing, and anything abnormal.  Maybe even try swapping the probes around (remember to relabel your panel, otherwise you will be very confused.)  Are your temp readings matched with the engine off?

I got the same advice from the LML about spark plug insulators and issues associated with timing - I just changed both spark plugs as a precaution.  Granted, I'm running automotive plugs and that was about a $4 solution...but at least inspect them closely.  

Best of luck.

Louis