I didn't say game-breaking. I said quest-breaking. There is a difference. With one, I can continue to play the game with the caveat that I won't be able to continue that quest. The other - I have an expensive paper weight.
Here is the latest example. In the quest Daedric, during the Dreamstride Portion quest of the Waking Nightmare, when saving the game automatically or manually, the game will freeze on consoles or crash to desktop on PCs. A patch was created to fix this error. (http://www.uesp.net/wiki/Skyrim:Waking_Nightmare
You may be one of the lucky ones who didn't experience glitches. If you do experience a glitch, go to www.uesp.net/wiki
. They list all the known glitches for this game.