Actually, what you remember were two dinners on Minbar, spread out over two different episodes, and only one involved Vir. The first dinner was with Delenn and Sheridan and Londo, a few months after Londo was named Emperor and got the Keeper. That was when Londo was forced by the Drakh to give the urn with the hibernating Keeper as a gift. The second dinner, and the "toast to absent friends" takes place 20 years after that, just before Sheridan's death; Londo has died a few years before, Vir is now Emperor, Centauri Prime has been freed of Drakh influence, and John and Delenn's son, who did open the urn on his 18th birthday, is safe again (though the story of how all of that happened was not told in the show, only in the novels). So no, Vir has never been under Keeper influence.