I just finished my Ultimaker and in the process of tuning the plastic feed, it stopped feeding at all. The feeder ground into the side of the filament, and as reported here I could barely push it by hand.
When I first got it working, I had to tighten the thumbwheel with what felt like a lot of force, or it would not feed. Now after printing only four objects (3 test 2mm cubes and a whistle) it stopped feeding 1/3 of the way into another 2mm test cube. It just chews into the filament.
Does the PTFE tubing stay in the stock fittings? If not, what did you use?
Edit: I'm using Cura, and this is the version of the feeder that is an allen head bolt.