EXCLUSIVE: Showtime’s flagship drama Dexter opened its sixth season on Sunday with a stellar 2.2 million viewers, up 24% from last year to mark the hit series’ highest-rated premiere ever and Showtime’s best original series opener in at least 14 years. But the prospects of the hit drama going to a seventh season are now uncertain as negotiations between Dexter star Michael C. Hall and Showtime have broken down. I hear that the two sides reached an impasse yesterday, the same day Dexter‘s big Season 6 premiere ratings came out. Hall’s contract for Dexter is up after the current sixth season, which is about to wrap production. He has been negotiating with Showtime for a while, but I hear talks broke down after the two sides couldn’t bridge a $4 million gap in proposed salary for a new deal, with Showtime offering $20 million for two more seasons and Hall’s team asking for $24 million. Either figure would make Hall one of the highest-paid actors in cable. Sources indicate that the network brass remain hopeful about reaching a deal, with signing Hall for one more season vs. two also an option. Hall jumped on Dexter immediately after finishing Six Feet Under and, after working on a TV series for 10 straight years, the actor had been looking to do other things, including a Broadway musical. He won a Golden Globe for his role on Dexter last year.