XK8 - "ENGINE FAILSAFE"

[K.K.]

Has anyone had this come up on the dash "ENGINE FAILSAFE - No Trac Available" and the car cuts out to about 10mph. I had this problem in my XK8 about a year ago, had it fixed (was just the computer needing to be reset), happened again 3 months ago, had it fixed (this time they said it was a computer/throttle problem). Anyway I have recently sold the car to my brother (who knew all about the problem - plus with an unexpired warrenty, fortunately). He called to day to say that the ENGINE FAILSAFE is up to its old tricks again. Does anyone have any ideas as to what this could be?

Thanks
KK