Federal agents arrested a 79-year-old Hartford man, Robert V. Gentile, Friday in connection a $500 million art theft from a Boston Museum. The man's laywer, A. Ryan McGuigan, alleges his client knew nothing of the theft which occurred 25 years ago. "It's the same F.B.I. guys doing the same thing as last time," he said. "They won't stop squeezing my client." A federal prosecutor said investigators had a recent recording of Gentile discussing the sale of the stolen paintings.