Game unplayable - interface problems

I’ve just purchased the expansion and the game is unplayable.

The in-game fonts are extremely small.

Items on the ground are not visible.

I can’t equip any items, or click them in my inventory.

The settings panel is rendering way off to the right and massively oversized, with the scrollbar and buttons displaced.

Same for the potion bar in-game. The UI is completely messed up.

I would appreciate some help, or at least a refund.