i just completed Blood's Honor, at which point Purity of Revenge should start immediately. however, nothing happens. Vilkas (i believe it's him) just mentions that we go finish off the Silver Hand and simply sits down. i can not at all figure out how to get the quest to activate. i've reloaded, replayed in several different ways. the only thing i can possibly think of is that i participated in the siege of Whiterun and that this has somehow effected my quest. please please please help

It seems to me from my experience with the companions and the quest line, that this quest line and the people involved in the guild and quests are very buggy.

I married a person from the companions, and after having her follow me then dismissing her I can no longer get a follower.
I have the same quest from a member that fails each time because I have a ghost follower that will not go away. Several other people have reported bugs with the followers, and companions quests.

hrm, at least i know i'm not the only one. is this the kind of thing that they fix with time? i really feel like just shelving my character now, honestly. i've made the companions the focus of my questing and now it seems as though i'll never be able to complete their quest line.