The Walktrough is bang on with one exception...the third door on the right is not the one you take the phlactery to...it is one of the doors to either side of it...I forget which, but I am pretty sure it is the second door on the right from where you enter the Hall! Kill the Lich, get the phlactery if you don't have it already, and take it straight to the second door or the fourth door on your right....and all is well. When that gets done, the Lich is a goner! Then you go back and talk to the ghost, and you find the key to the end door to Wyrms tooth exactly where the walkthough says it is.
You are most likely going thru the wrong door. As to why Bandoth does not take the Razorvine is beyond me...he bloody well should!