and also why Logan was dying. I know he said something about being poisoned by the adamantium.
As he stated, his healing factor wasn't working so well anymore. And as you'll recall, the healing factor is what allowed them to put the adamantium into his body. (The idea being that putting metal throughout any normal persons body would kill them.)
So with his healing factor not working so well anymore, the adamantium was starting to damage/weaken/poison/eventually kill him.
So with his healing factor not working so well anymore, the adamantium was starting to damage/weaken/poison/eventually kill him.