I had a breach failure as well.  Attached is a link that focuses on this issue.
http://www.thehighroad.org/showthread.php?t=228839&page=2

My post is # 37 and there is a link to pictures.

Long and short of it...

I dry fire practiced A LOT w/ that pistol with the advice that it didn't need Snap Caps to dry fire with.  I easily put 10k dry fires on that pistol.  One day, during dry fire, I pulled the trigger and something didn't feel right.  I couldn't retract the slide.  Finally pried it open and noticed the breach face was blasted outward.

Called Glock and it was obvious in conversation w/ the rep, that this wasn't a one off problem.  They were good about it though.  They gave me a new slide and moved the Trijicons from the old slide over to the new.
Unfortunately, they replaced some of the trigger internals ......the really nicely worn in and smooth internals .

Anyway, I still continue my regimen of dry fire, but now use some kind of snap cap.

THIS!

Dry firing does not hurt. I've talked to a glock representative and they said it's a go. However if you want to get better at shooting and seeing if you having problems with trigger control or anticipating shots get snap caps and load them with your regular rounds. You'll learn really fast and probably more efficiently then just plain old dry firing.