dekane mines - can't enter

I'm not sure why, but I can't enter the Dekane Mines, the dungeon near the crane machinery monsters.

I have all prerequisite quests completed (so I have the entrance card), I go to click on the lever and nothing happens.

I have the lever targeted, but after clicking it, the targeting goes away (the target arrows disappear even though I haven't targeted anything else or manually untargeted by pressing the escape key).

Thanks for any help and/or advice. ^__^