I don't think money is the root of all evil; I think wanting is. It seems to me that when I am unhappy, when I feel discontented, it is almost always because I want something I haven't got. I chafe at my older model car, because I see all the shiny new ones. There is nothing wrong with my car. Nothing. I just suddenly value it less, judge it more harshly, because I want a new one. I see someone's vacation pictures, and suddenly feel stifled by my job. I want a book or a CD or a new movie. I start resenting the money I have to spend on the dog.
Wanting what you haven't got, you become a judge, weighing what you have against what others have. You become resentful, because you are so deserving, and others, who deserve less, have more. You become selfish, because when you focus on your own wants, you have no room for others.
This kind of want, that doesn't stem from true need, is destructive, seductive, powerful, but ultimately, unfillable.