I would also concure with the suggestion that you may be getting bacterial contamination by the use of plates not cleaned off and returning the cooked product to the same plate it was brought to the grill on. That is really a BIG NO NO. I suspect that you may have been dealing with some poultry. As outlined in Steves new book Keep it Hot, Clean And Lubricated (Page 24). You ak=lso may not be getting the internal temp high enough to kill off those little kritters that will make you deathly ill.A good themometer will assist you in determining the internal temps.