Ra9000: it did'nt work for me.
Btw. only one character get main quest or all? When I look in to first character in the Quest section, there is Garreth quest, but only one character.
Maybe animation is not showed when I get out from Inn?
Sorry to hear that your problem persists. The animation starts immediately when you leave the inn with your new party in a fresh game (this is probably what the "revert game" option in the inn fixed for me).
I'm not sure if only the main character or all characters get the main-quest, because I am playing a solo character. But how did you get the quest if Gareth never appeared?
What i did precisely was: go to the inn (before loading a game), press the blue "revert game" symbol there on the left, create a new character and then leave the inn.