I am stuck in the room with the closed iron gate and two red crystals.
I use Jak's boots to jump up to the ledge and press the button. I then run over to the other button and press it. no matter how many ways I try I cannot get the iron door to open.
First, you don't have to press the buttons.... You can just jump to the area you need to be to shoot the arrow from. Practice with cheap arrows until you hear the "thunk" - don't move your aimpoint, equip the arrow of extrication, then use it. No problem.
Don't know what to do if it won't let you fire it. Didn't happen to me. Try equipping/unequipping several times. I'd say drop it and pick it up but I don't think it will let you do that.
Ah, Freeze/sins_to_dark you might have missed it, but you need to hit the keyhole with a normal arrow first before you can equip the arrow. Didn't know that myself as I didn't try to equip it until I'd already hit the hole with a normal arrow.