Vince is the name of a character in Facade. Grace had an affair with him after Trip proposed to her; this has lead her to believe that she jinxed their marriage. Grace can be persuaded into admitting that she kept seeing him for some time after the wedding. Not much else is known about him, as he is only mentioned and never seen.
Mentioning his name can cause Trip to eject the player from the house. This depends on a number of things mainly being Trip's mood, if he is happy (like when the player first arrives, or he is fixing the drinks) he may attempt to laugh it off saying he doesn't know any Vince. If he is in a bad mood (for example if the player has been annoying him, or he is fighting with Grace), he will eject the player from the house.