So before shadowlabs this weekend, out of nowhere, my WoW client crashed on me.... 8 times.   Too make a long story short, chances are its Quest Helper.  My fiance who has a lvl 40 can still run Quest Helper, so it doesnt like some lvl 70 quests from what I have found.  Some forums show that adjusting 2 lines of code can fix it, but in my case this did not work.  Right now I am running WoWmatrix and waiting for the latest update, however for me at least none of the latest versions are working.  I will let yall know if this changes in the future, but at least I can save you a fustrating weekend.