Question regarding to a recent R22 crash with failure autorotation

Hi

I am a fix-wing guy. I read about a recent R22 crash in AZ.
http://www.ntsb.gov/NTSB/brief.asp?e...28X00255&key=1

I have question that was it the limitation of the R22 caused the
accident, or the pilot failed to, or made serious mistake that causes
the blade stop?

I read about a very good discussion at this group (posted in 2004)
regarding to R22 autorotation.
http://groups.google.com/group/rec.a...e010bbfd0d2fcf

However, I still don't understand much because I am a fix-wing pilot.
Can anyone point me out why the blade would stop? Is there any online
introductory reading regarding to autorotation?

This kind of blade-stopping-accidents scares me to even try a
helicopter flying. I hope any of you could give me explanations that
help me understand helicopter more.

Thanks in advance.

jpskies