Does running the game at too high a framerate or something break the AI? I can't even order my tanks to destroy a static building without them messing the order up and parking right next to the building, letting themselves get blown up.

You have to hold Left Ctrl and then issue the attack on the building. You will notice the cursor icon will change when you hold Left Ctrl down.

I think you can also click one of the attack options on the menu for a unit to tell them to force attack but ether way, you must do it manually. Simply right clicking on on a building won't work. Unless maybe the building is occupied by infantry.

You can also force move your infantry into a building or trench that is being occupied by enemy infantry with Left Alt. A lot of people don't know about this, particularly forcing your guys into a trench to fight the enemy.