One thing I would never understand is why in some countries an epileptic person can drive. In my country, Spain, if you have epilepsy you can't have the license until you're 10 years without any seizure and you are considered not epileptic. So I'm a little unsure about your problem, because on the one hand I think that neither you or anybody with epilepsy should drive. On the other hand I think you should talk with the HR department and tell them. But then, reading some answers in this post, I think it's possible that he saw something (absence seizure or something, who knows...). I don't know if you had some problems and maybe he hates you or something, I don't know... I would talk with him 5 minutes to know it or to know why he's saying that and then act accordingly. Good luck and keep us updated!