Perfect Hollandaise every time using a blender/food processor?
I have used the exact same procedure that you describe on a number of occasions, and the result has always been a thick butter-like consistency, and I think that this is pretty much unavoidable when using a food processor. Maybe you can get a thinner consistency if you use the whole egg like ElendilTheTall suggested. 

Anyway, since the sauce never emulsified, I think you have been pouring in your butter too quickly. It is important to just add a few drops at a time until the sauce has started emulsifying. After that you can go faster, but it should still only be a thin stream. 

Also, something that I have noticed is that when using a food processor with only a small amount of egg yolks (or any ingredient, for that matter) is that the rotating knives will actually rotate above the ingredients and not actually mix them. When making hollandaise/mayonnaise, that will be fatal since you will just be pouring butter on top of a thin layer of egg yolks. So you might want to check your food processor and see if it works similar to mine. 

While I realise that you use this recipe because it is easier than making hollandaise by hand in a bain-marie, I would suggest that you at least try making it "for real" once before settling on this method. The consistency is so much nicer. I think the flavour is better too but that may only be my imagination.