Well, the kind thought is that he was in a suspended animation mode. However, if I remember right he made comments about his time in the coffin, which leads me to believe he regained consciousness each evening. Either way there are leaps to make. If he was suspended why did he "wake" up to lead Willie to his coffin? Willie definately appeared to be under Barney's influence, staring at his portrait and so on. Though I guess you make a point for that being greed alone.
If he was alert throughout, why didn't he lead someone to him sooner? Can a vampire exist indefinately without any blood?
Regardless, he certainly got up and out of there in a one cranky mood. Can a vampire get up on the wrong side of the coffin?