It's not just Luongo. The entire Vancouver team looks completely lost when they play in Boston. Can't do anything on power plays. Give up the puck constantly around the goal. Let guys hang out around the net to tip pucks past Luongo. Luongo has looked bad, but no on Vancouver has looked good in Boston in my humble opinion.
One complaint Vancouver had when playing in Boston was the temperature of the ice was not working with them. In the earlier games in Vancouver, the ice conditions and temperature were colder than that of Bostons. Now, we do have to realize that the Boston area went through storms followed by hotter days than they planned for but for the most part the hotter the ice surface, the more tendancy for the puck to bounce and flip around.
Oddly while watching game 7 (via the NBC feed), Piere Meguire mentioned the temperature of the building was getting hotter than normal. He didn't mention it for any of the other Vancouver home games for the series and the West Conference playoff rounds. This may seem like a pointless advantage for Boston but remember that Vancouver is used to playing on a colder ice surface than the one in Boston and Boston was not used to playing on the colder surface in Vancouver. Its minor but it does mess with some players and on a stage that big, all the little details are bound to catch up.