i was riding from haven to crossing... and this happened to me:

[North Road, Plains]
Turning your back to the massive obsidian wall to the south, you look out over a broad valley stretching below you to the north. For miles around, the bare sterile earth is a dull rusty red, scattered with grey and black boulders of pumice and basalt. Far off in the distance, you can just make out the silvery reflection of water, and even a hint of green. You also see a flea-bitten dun pony which you are mounted on and a tunnel cut into the obsidian ridge.
Obvious paths: north.
>You can't ride your flea-bitten dun pony in that direction.
>The ground beneath you begins to tremble, rising in a terrible crescendo until it seems that the whole world is screaming. You struggle to maintain your balance and sanity until finally it stops.
You lose your footing and fall to the ground.
>dance
You can't do that while mounted.
>go tunn
You must be standing to do that.
>stand
You stand back up.

i was unmounted when i stood back up... hmmmmmmm