Yahoo! Answers - how did bruce lee die?
Rumors are that, just rumors. The first answer in this link should give you the info. Here's a quote:
"After a lengthy coroner's inquest in Hong Kong. A panel of medical experts eventually concluded that Bruce Lee had died from a hypersensitive reaction to a compound in the drug Equagesic. This hypersensitivity led to a swelling of the brain and resulted in Bruce Lee entering a deep coma from which he never awoke. The coroner declared himself satisfied with the finding, and so did Linda Lee, his wife. "
Reaction to a "super aspirin" caused his brain to swell and made him go into a coma like state. That's what the coroners said, that's what I believe. Unless someone can say they were there or have documented proof.