XT Rear Derailleur Alignment with chain

Quoted post said:

Originally posted by David
My front XT derailleur got caught on the chain the other
night, and after repositioning and readjusting it, I notice
that I get a clicking noise ever half chain revolution or so
from the rear of the bike.

When I turned the bike over I could see the rear derailleur
arm (XT) was not aligned with the direction the chain was
running in, and so every so often the chain jumped from its
guide wheel. It happens with the large front cog and the
larger rear cogs selected.

I know little about bike mechanics, but any advice would be
useful. I cant tell whether the whole housing is moved, bent
, or whether just the arm is bent.

Can anyone point me to some diagrams/pictures that show
correct alignment and how it measured ?

Any help appreciated Dave

http://www.parktool.com/repair_help/FAQindex.shtml
Scroll down to Derailleur and Shifting (front and rear) section.
You might have a bent rear derailer and or hanger.
Take a close look at your chain rings, as at least one of them sounds like it is bent.