Bloody trees, the downfall of many remote control aircraft. But you did record the crash on video though? Bloody good thing it didn't fall out of the tree, a 35 metre fall with the transmitter off would have done a bit more damage that a few props.
I'm thinking about getting prop guards. They have saved the props on my Kogan UFO quad heaps of times. Just ordered some undercarriage, should have got prop guards at the same time.
What I've noticed with the UFO is when the prop guard hits an object the rear of the quad flips up towards the object so that it is 90 degrees to the direction of travel. Flying the quad around my front yard I,ve hit gutters on the roof (which you can see if that video I posted on the RC Cars thread very early in the vid), trees, the wifes car (don't tell her), and scared the crap out of the cat.
I've got about 100 acres of reserve directly out my back yard. Once I master the basics, I'll be hopping the fence and flying out my back yard. Most of it is relatively treeless.