A child advocacy group found that states across the country have lost track of tens of thousands of rapists, child molesters and other sex offenders who are supposed to be registered in Megan's Law databases, according to a startling new survey.  After an Associated Press investigation that revealed California had lost track of a least 33,000 sex offenders, Parents for Megan's Law contacted all 50 states to ask about the accuracy of their registries.  What was found was that states on average were unable to account for 24 percent of sex offenders supposed to be in the databases.  Nineteen states, including Texas and New York, said they were unable to track how many sex offenders were failing to register.  They're implementing Megan's Law, then turning their backs on it, said Laura Ahearn, executive director of the nonprofit agency in New York.  They need to technology and the staff to track down their sex offenders.