Hi BigggDaddy:

I don't think Aspartame has ever had to carry a warning label- I think you are thinking of Saccharin, which the site below said was found in some 1970's studies to cause bladder cancer in rats. The government made the manufacturer put warning labels to that effect on Saccharin products, but these were removed in 2000 after scientists couldn't prove it was harmful to humans.

This site says that the only warning on aspartame is for penylketonurics or people with liver problems who can't metabolize an amino acid found in aspartame.

http://www.youcanbefit.com/sweet.html

I found this article to be very fair to both sides on the sweetener debate.