I'm stumped ...

... that a stump could do this kind of damage. On my June 26th ride on Al's Trail I mentioned that hit something that knocked my chain off. I thought it was a stump because when I came down the berm there was a stump really close to the trail and I thought I hit that because it didn't make a scraping sound that you would think you would get with the derailleur hitting a rock. Maybe it was a rock afterall?

The reason I think I might have actually hit a rock can be seen in the following pictures. A stump couldn't have caused that type of stress in a machined piece of aluminum. In the first picture below, the hanger in the back ground is seen pushed back. Not sure what you call it, but poking around the Wiki, I think what you are seeing is sheer stress on the portion that hangs down for the derailleur.

And I think what you are seeing here is an example of normal stress, in which the blade was bent perpendicularly to the plane of the hanger.

I am wondering since I was having problems shifting in the past that the hanger suffered an earlier incident and when I took the bike in for a tune-up, the shop made the corrections to the derailleur to compensate for the changed aspect of the hanger. Then when I hit again, the aspect changed all over again and trying to compensate for this new position is too much for the H and L screws to handle.

I had a similar situation with the Fixation where the hanger was bent in towards the gears and I could never get the bike to shift properly again. I put the new hanger on and I will test the bike this weekend to make sure it's in good working order. I think I am going to order a few extra hangers, too, and keep one in Camel for when I find myself on an epic ride and this happens.