I have had some odd glitches in cata that I suspect are driving WoW GM mad from my tickets, my all time top one is the fact I cannot enter dungons/instances such as Stonecore and Vortex to pick up/hand in quests. AS I get to the entrance it tells me to enter heroic dungons, I must be lvl 85. ANyone else had this and how did you fix it (note I said 'you fix' as Blizzard has still not managed but are trying very hard).
I know I sometimes have that problem (or similar)on my warrior - one with stonecore is kinda annoying. Works both alive and dead - when I go to fly into say, stonecore, sometimes the portal and the summoning stone disappear so I am unable to enter then instance as if it's phased. So I have to approach it at a low swooping angle, and try and quickly sneak my way in via the quickest route.