Freeport-McMoRan Inc. (NYSE: FCX), one of the world’s largest copper miners, has just been hit by another big problem that could take down its Grasberg mine in Indonesia, a key asset. That’s come just as the miner was starting to make some real headway on the debt and oil fronts, two other issues that have been dimming its outlook. Although Freeport is likely to muddle through all of this, these are the three biggest challenges the company is facing today.