I logged in today on this character Jonblikk and was in Tuanka village in Borean tundra. I mounted up on my swift flying , mount, flew over to near "The Dons of the Dying" area , accepted a quest from the sagemistress near the road, dismounted, killed the plaged magnataur to complete the qoest, attempted to remount and it didn't work. It showed the casting bar while attempting to mount, heard the windrider's roar and saw it for a split second, then was instantly dismounted. Same thing happens when I try to use my land mount. Flew to Dalaran to move completely out of the area and I still couldn't use air or gorund mounts without the same thing happening.

I exited the game, logged in again this time in dalaran. I was able to mount. I dismounted and tried to remount and the same thing happened, coundn't remount.