Can a minor acetaminophen overdose (taking five extra-strength tylenol at once) cause a problem?

No. Assuming you're >12 years old, don't have aids, alcoholism, or other chronic liver disease, you should be okay. For anyone interested in learning everything you wanted to know about tylenol (acetaminophen) overdose, but were afraid to ask, please direct your web browser to: http://www.Tylenolprofessional.Com/assets/overdose_monograph.Pdf.