Tamer/pet bug. Read if you are a tamer.

[Tjalle]

http://stratics.com/threads/warning-do-not-give-a-follow-command-while-riding-tamer-pets.382820/

Apparantly there is an issue where mounted pets go wild if you give the "All Follow" command to another pet of yours.
Click link for more details and updates.

[Hoffs]

Thanks for the notice.

[Zardoz of Crete aka Kimi aka Victoria Secret]

Saw this first hand on Sonoma with a fellow tamer, his Nightmare went wild with him on his back, he had to retame

[Blind Otto]

I wonder if this explains my skittish horse at the tournament last night?
I was doing nothing, yet, as long as I tried to make it stand in one particular spot, it kept turning south-west.
Or perhaps the arena was simply haunted.

[Map]

They are saying the bug was fixed with the patch that went out on Feb 9th.

"The Bug fix will go in at shard maintenance on the 9th Read the patch notes!"

yeay

[Zardoz of Crete aka Kimi aka Victoria Secret]

Guess I will check this out with a horse