I believe there are several reasons for Carnival dropping Antigua. As somebody who lives on the island let me give you a brief run down of the last 14 months.
July 2008 British honeymoon couple Benjamin and Catherine Mullany tortured, beaten & murdered in their hotel room. Rumours were later started by persons unknown that the couple who were a doctor and Physio therapist by trade were dealing in drugs. It is well known this rumour was started by members of the Antiguan government in an effort to deflect blame.
January 2009 Captain Drew Gollan murdered in front of his girl friend and their daughter at English harbour. Again rumours were spread about possible links to drug smuggling.
February 2009 Allen Stanford's massive fraud becomes front page news. Leroy King administrator for the Antigua governments Financial Services Regulatory Committee is later indited by the US government for covering up the fraud.
The Antiguan government have since seized Stanford's properties and assets on the island and refuse to hand them over to the US receiver. They have also made it clear they do not intend to pay for the property so depriving Stanford's victims of any chance of recovering any part of their life savings.
Local radio station crusader radio has phone in where locals brand American depositors in Stanford's bank "greedy" and deserve to lose their money.
2008 saw 19 murders on an island 10miles x 14miles giving it a higher murder rate per head of the population than New York. Rapes are running at around 30 per year, and that is only the reported figure. All of which is deliberately hidden from tourists visiting Antigua.